Over 100 million people, and more than 30% of adults, suffer from some type of allergy in the United States, and that number is on the rise. But where are these allergies coming from? Do we inherit them, or do they result from environmental factors?

The answer involves a little of both, said Dr. Derek Chu, an allergy specialist at McMaster University in Ontario. Allergies occur when the immune system mistakes a harmless substance, such as pollen or a certain type of food, for a dangerous substance and attempts to get it out of the body. Once the body reacts this way toward an allergen, it will repeat the allergic response for every new exposure, unless there is a successful intervention.

"The body goes awry and is trained to do the wrong thing," Chu told Live Science.

According to Leah Kottyan, an immunologist at Cincinnati Children's Hospital, there are several main types of allergies. They include allergic dermatitis, which manifests through skin conditions such as rashes and hives; allergic asthma, which involves airway inflammation and the overproduction of mucus; allergic rhinitis, which results in sneezing and a stuffy nose; and food allergies, which can trigger a whole-body immune response. All of these responses could be driven by the same allergen, Kottyan noted. Moreover, people who have one type of allergic response are more likely to have others and more likely to be allergic to more than one thing.

According to Kottyan, there is almost certainly a genetic component to the development of allergies. Independent studies comparing the prevalence of allergies in identical and fraternal twins found that the identical twins were far more likely to exhibit similar allergies than the fraternal twins, indicating that their genetic makeup played a role. In one study, the identical twins had an average of 95% similarity between four different types of allergies, whereas fraternal twins had an average of around 37%.

However, the link between genetics and allergies is complicated. Allergic responses can be traced to mutations in hundreds of genes. One of the most studied such genes, known as filaggrin or FLG, affects the development of the skin's moisture barrier, Kottyan said. Mutations in FLG cause the moisture barrier to not act as it should. This increases a person's risk of developing eczema, allergic dermatitis and other types of allergies.

FLG mutations can put the skin in a compromised state, which can increase the skin's susceptibility in getting cuts and scrapes and from developing dry and cracked skin. When this compromised skin comes into contact with an allergen, the immune system is more likely to become sensitized improperly to that allergen, Kottyan said. This can cause an allergy to develop.

"Literally, when there's food on the baby's skin, the food is coming in through the damaged skin barrier, and the child is getting sensitized to that food through the skin," Kottyan told Live Science.

Environmental factors

Although allergic reactions have a genetic component, environmental factors — including exposure to different allergens — play a big role in how someone develops allergies.

"It doesn't track one to one," Chu told Live Science. In a recent study Chu co-authored, scientists investigated nongenetic risk factors for allergies, including the baby's method of delivery, early exposure to antibiotics, and when they were introduced to solid food.

Moreover, even people who inherit a tendency to develop allergies may not be allergic to the same things as their parents. Rather, whether the baby becomes allergic to peanuts, for example, will likely be determined by their early exposure to that allergen. There is now a FDA-approved immunotherapy treatment for children that centers on daily exposure to peanut proteins over a long period of time.

"If the immune system is exposed inconsistently, then it's not learning to tolerate what it's being exposed to, and instead it can easily end up misbehaving, leading to allergic reactions," Chu said.

The microbiome also plays a big role in the development of allergies. Scientists have found that early exposure to a wide variety of environmental microbes results in robust and healthy gut and skin microbiomes that are more tolerant of potential allergens. Without this diversity, or with a microbiome consisting of higher percentages of certain microbes, it is more likely that a person will develop conditions like eczema and food allergies.

A similar theory suggests that the eradication of many common parasites, and the more sterile environment many of us now live in, may have played a role in the uptick in allergy cases in the United States. With no parasites and fewer viruses and bad bacteria to go after, our immune systems may be developing too many allergy-fighting cells instead of the bacteria and virus-fighting ones.

Researchers like Chu and Kottyan are continuing to pinpoint the risk factors that can cause someone to develop allergies and test new preventive measures to help children grow into allergy-free adults. For now, Kottyan said, the best steps parents can take to prevent allergies in their children is to expose them to common allergens early and often and to take good care of their children's skin, especially in areas that are prone to dryness and eczema.

"Allergy genetics are not deterministic; they aren't going to say you absolutely are going to get a disease," Kottyan told Live Science. "It's not a life sentence."

This article is for informational purposes only and is not meant to offer medical or dietary advice.

While spring is a lovely time of year to look forward to, for some, it brings about mixed feelings because their hay fever symptoms increase as the weather improves. Hay fever often leaves people with a runny nose, itchy eyes, sore throats, coughs and sneezes. However, there are things you can do to reduce how much pollen impacts you at this time of year, so here are our top five tips on how to survive hay fever season.

We spoke to Melanie Carver, chief mission officer of the Asthma and Allergy Foundation of America (AAFA), who offered some expert advice and tips on how to survive hay fever season. One option is to consider one of the best air purifiers to keep the air in your home as clean as possible.

Read on to find out what advice the experts give.

• Related: Best air purifiers for allergies 2026: Breathe easy this spring
• Related: Best air purifiers for pet owners 2026: Remove pet dander, hair and odors

Keep your windows closed

As soon as spring hits, it's tempting to open the windows and let the fresh air spruce up your home, especially if it's been a long, cold and wet winter. However, for those who suffer with hay fever, this may, in fact, be encouraging those allergens into the home. Pollen travels through the air, so if you open the windows, pollen can enter the home and increase the occurrence of sneezing, itchy eyes and coughing.

Melanie Carver, chief mission officer of the Asthma and Allergy Foundation of America (AAFA), explains: "Open windows, even windows with screens, allow pollen to enter the home easily, especially during times when pollen counts are high. Individuals with pollen allergy (tree, grass, and weed pollen are the most common) may experience allergy symptoms if the pollen that triggers their allergies is present in the home. Symptoms may include a runny nose, a stuffy nose, sneezing, itchy and watery eyes and coughing/wheezing.

"One of the best ways to manage pollen allergy symptoms is to reduce exposure to pollen. This means keeping windows closed when pollen counts are high and taking steps to prevent pollen from being in your home."

While keeping your windows closed in the lovely spring weather might sound annoying, especially if you want to freshen up your home, keeping your windows closed can have other benefits, such as keeping the warm air out of your home and helping to keep it cooler if it is a particularly hot season.

Use an air purifier to remove indoor allergens

If pollen does get into the home (which, to some extent, is inevitable), the best air purifiers can help remove these allergens and make your indoor space more pleasant during hay fever season.

Air purifiers work by using fans to draw in the indoor air and then passing it through a filter, effectively removing the allergens. The filters trap microscopic particles such as pollen, so these particles never reach your lungs. By removing these particles from the air, this can also reduce the amount of sneezing, itchy eyes and coughing you experience during hay fever season. Our top tip when buying an air purifier for allergies is to get one with a HEPA filter — these are the most effective filters.

Our expert, Melanie Carver, said: "HEPA – high efficiency particulate air – filters are an effective way to reduce exposure to common allergens, including pollens. HEPA filters work by using a fine two mesh of fibers to trap particles (such as pollen) and prevent them from being redistributed into the air. Asthma & Allergy Friendly® Certified air purifiers or air filters with HEPA can help reduce your exposure to allergens and airway irritants."

Change your clothes when you get home

To some, this might seem a bit extreme, but pollen and other allergens can get trapped on fabrics while you're out and about. Pollen is an airborne particle, meaning it moves around in the air, but it also attaches itself to various surfaces once it comes in contact with them. Therefore, changing your clothes when you get home can reduce the risk of further irritation to your respiratory system later in the day.

As pollen can also get trapped on your hair and skin, it isn't a bad idea to shower and wash your hair upon returning home for the day, either.

"AAFA recommends changing clothes after you’ve been outside on high pollen count days. This is one way to help reduce your exposure to the pollen that may trigger your allergy symptoms," said Melanie Carver. "Put dirty laundry directly into your washer, or at least not in your bedroom. We also recommend washing your hands as well as washing your hair to help remove pollen. For people who can’t or don’t want to wash their hair that often, use a hair covering when outside to prevent pollen from collecting on one's head.

"Additionally, we recommend wiping down your pets when they come in from outside to help keep them from spreading pollen around your home — and when possible, bathe them once a week," Carver said.

Dry laundry indoors

Similar to changing your clothes upon returning home, it's a wise idea to avoid drying your laundry outside during hay fever season.

In much the same way as pollen can attach to your clothing when out, it is the same if you dry your laundry outside. You are leaving your clothes prone to that transmission, which will then come into your home and into your wardrobe or cupboard. By drying your laundry indoors, whether that be on an airer or in a tumble dryer, you will be reducing the risk of bringing pollen into your home and contaminating other surfaces and/or clothes.

"Like other small particles, pollen settles on surfaces and may become embedded in fabric, including carpet, curtains and bedding. It is important to regularly clean surfaces — wiping down hard surfaces with a damp cloth, vacuuming carpets and furniture fabric, and washing rugs and curtains," said Melanie Carver of AAFA.

Use a vacuum cleaner with HEPA filters

As we mentioned earlier, air purifiers are a great way to keep the air in your home allergen-free (or at least reduced). Air purifiers use HEPA filters to make sure this removal of allergens is effective, and some vacuum cleaners also use these filters to ensure effective removal.

Hoovers with HEPA filters work by capturing microscopic particles, such as pollen, by trapping these particles within the filter. Vacuum cleaners without HEPA filters may not effectively trap these allergenic particles and instead release them back into the air. Therefore, we recommend using or investing in a vacuum cleaner that uses HEPA filters.

"HEPA — high efficiency particulate air — filters on vacuums can be a useful tool in reducing pollen and other allergens from the home," said Melanie Carver.

"Taking care to change your vacuum cleaner’s filters regularly helps ensure they operate most effectively to reduce allergens. Many vacuums, even those with HEPA filters, stir up a lot of debris into the air. People with sensitive airways should consider wearing a mask when vacuuming or have someone without asthma/allergies do the vacuuming, while the person with asthma/allergies stays out of the room for several hours until the dust settles. For some people, removing wall-to-wall carpeting may be a better solution."

Melanie Carver also offered tips on what to look for in a vacuum if you are a hay fever sufferer. "When choosing a vacuum cleaner, look for the following," she said. "The vacuum must be proven to remove surface allergens, dust released when changing the vacuum bag or canister should remain low, exposure to allergens while changing the bag or cleaning the canister should be low, water-based collection systems must not negatively impact the relative humidity of the air and carpet and water-based collection systems must have a care code that emphasizes the importance of mold growth prevention in the collection system."

One of the best air purifiers is a worthwhile investment during hay fever season. They work by filtering the indoor air in your home, removing nasty particulates such as pollen. However, to ensure they can work effectively, there are certain things you need to do.

We spoke to Melanie Carver, chief mission officer of the Asthma and Allergy Foundation of America (AAFA), who offered some advice on the mistakes to avoid when using an air purifier to reduce hay fever symptoms.

Placing the air purifier next to an open window

For those with hay fever, an air purifier can make a big difference by reducing the amount of allergens in the home, including pollen. However, it's important to ensure they are used correctly so they are most effective.

During hay fever season, sufferers are advised to keep their windows closed, to reduce the amount of pollen that can get into the home. While you don't have to follow this advice, and may prefer to let some fresh air into your home, having an air purifier on while it's near an open window can mean that it can't do its job as effectively.

Melanie Carver, chief mission officer of the Asthma and Allergy Foundation of America (AAFA), explains: "When pollen counts are high, AAFA recommends keeping your windows closed. Placing an air purifier next to an open window will cause the device to filter outdoor air, meaning it will be less effective at cleaning the indoor air. Air purifiers have capacity limits and should only be used to filter air from appropriate-sized rooms."

Not changing filters

While air purifiers can do a great job of removing allergens from the home, it is important that essential maintenance is carried out on them regularly to make sure they are performing at their best. Part of this maintenance is changing the filters.

Each brand and model of air purifier will have its own recommendations on when to change the filter, and it's important that these are followed. An ineffective filter can mean the air purifier isn't catching as many of the allergens in your home as you think, and for hay fever sufferers, this can lead to more sneezing, itchy eyes and coughing than if the filter was effective.

"AAFA recommends changing the filter on your air purifier/air cleaner according to the manufacturer’s recommendations — usually once every 2 to 3 months," said Melanie Carver. "A dirty air filter is less effective and may result in allergens being sent back into the air."

Not running the purifier continuously

Air purifiers work best if you run them continuously. During hay fever season, this can be particularly useful as it means the air purifier can continue to circulate and filter the indoor air, constantly reducing the amount of pollen particulates within the home.

If they are only run for a few hours each day, they can not be as effective in ensuring the pollen level remains low. This is especially true if windows and doors are left open or pollen is brought into the home via clothes or on dog and cat fur, for example. By running them continuously, the pollen level will be managed much more effectively.

"Continuously running an air purifier helps remove pollen and other allergens from your indoor air. If you use a portable air purifier, you should place it in the room where you spend the most time. For example, in the bedroom while sleeping. Depending on the room size and the rating of the air purifier, it can take up to several hours to cycle through and filter a room’s air," said Melanie Carver of the AAFA.

Placing it in a corner

Air purifiers come in many shapes and sizes and can be effective for different-sized rooms. One top tip is to ensure you buy one that is suitable for the size of the room you need to purify. Another tip is to make sure you place it in a good location where it can circulate the air efficiently. Placing it behind or next to furniture, or in the corner of a room, can make it harder for the air purifier to circulate the air effectively, and to reduce the level of pollen within the space.

"AAFA recommends placing an air purifier in the room or rooms where you spend most of your time. For example, you should place an air purifier in your bedroom while sleeping to help reduce exposure to allergens," said Melanie Carver.

"When choosing a location for your air cleaner, you want to put it somewhere that supports optimal air flow. Putting it behind a door, piece of large furniture or against a wall will obstruct the air flow. Choose an open location about 1 to 3 feet from obstructions and elevated up off the floor for better circulation.

"When using an air purifier, it is important to pay attention to the CADR rating. CADR stands for Clean Air Delivery Rate and indicates how effective a purifier is in removing air pollution from a room. Placing an air purifier in a room larger than its CADR rating will reduce its effectiveness. Additionally, air purifiers that earn the Asthma & Allergy Friendly® Certification meet strict scientific standards for reducing allergens and for ensuring that allergen reduction is the result of removal rather than just redistribution."

Not cleaning other surfaces

Yes, air purifiers can work well to remove allergens from the home, but the purchaser also has to take some responsibility in ensuring their home is kept up to a habitable standard.

Air purifiers work by filtering the air, so if surfaces are left dusty, there is more dust that can be moved around the home. This makes the air purifier work harder — it will be constantly battling to try and filter the air. Similarly, if surfaces are not kept clean, pollen particulates can attach themselves to surfaces, meaning no matter how hard the air purifier works to try and bring the level of pollen down within the home, it will always struggle to do so.

"Keeping surfaces clean helps reduce dust and pollen that may become airborne," said Melanie Carver. "These are tiny particles that get picked up into the air by walking by, using a vacuum, blowing a fan or air cleaner or even cleaning. One of the best ways to manage allergies like pollen or dust mite allergy is to prevent, capture and remove allergens that may collect in your home. Keeping surfaces clean helps reduce how much work an air purifier needs to do to filter your home’s air — it will also prevent premature filter clogging and extend the life of your air filters/machine."

A New Jersey man has died in the first documented fatal case of alpha-gal syndrome, a meat allergy triggered by tick bites.

In September 2024, the 47-year-old man collapsed and fell unconscious around four hours after eating a hamburger at a barbeque, doctors wrote in a report of the case. Despite attempts by the man's son and paramedics to resuscitate him, he was declared dead later that night after being transferred to a hospital.

The case report authors, who published details of the case Thursday (Nov. 13) in The Journal of Allergy and Clinical Immunology in Practice, wrote that it was important to document this deadly case because many U.S. doctors remain unaware of alpha-gal syndrome — even as the ticks that most often spread the disease move into new territory.

"We would argue that there is a major need for public education in areas where the tick is increasing," they said.

Alpha-gal is a sugar found in all mammals except for humans and other primates. In alpha-gal syndrome, the human immune system overreacts to this sugar, causing symptoms that can range from mild to life-threatening. These symptoms can include hives, vomiting, stomach pain, difficulty breathing, blood-pressure dips, dizziness, and in the most severe cases, anaphylaxis.

Tick bites can trigger this allergy to alpha-gal because they expose a person to the sugar via the tick's spit, setting off a chain reaction that leads to a hypersensitivity to the sugar — in other words, an allergy. So the next time a person consumes a product containing alpha-gal, their body overreacts, even if they safely ate that product many times prior to being bitten by a tick.

Beef, pork, lamb, venison and rabbit meat carry a high concentration of alpha-gal. In addition, milk products and products derived from mammals — such as gelatin, lard and gravy — can also contain enough of the sugar to trigger reactions in some people with the syndrome. Non-mammalian animal products, including poultry, eggs, fish and seafood, do not contain alpha-gal.

In the New Jersey man's case, his alpha-gal syndrome may have gone unnoticed because his family typically ate chicken, the case report suggests.

A few weeks prior to his death, the man went camping with his family, and on the trip, they ate beef steak for dinner. About four hours later, he developed severe abdominal discomfort and was "writhing in pain, having diarrhea and vomiting." His symptoms resolved a few hours later and he felt well enough the next day to go on a 5-mile (8 kilometers) walk and eat breakfast.

Two weeks later, after the camping trip concluded, the man and his wife attended a barbeque, where he ate a burger. Again, he felt fine for about four hours before developing gastrointestinal distress, and from there, his symptoms quickly progressed to anaphylaxis.

"The fact that severe abdominal pain without any other allergic features can be an important and indeed dangerous form of anaphylaxis is not well recognized," the case report authors wrote. When the man's body was examined shortly after death, the autopsy didn't turn up clear signs of anaphylaxis, and it was initially documented as a "sudden unexplained death."

After his death, the man's wife asked her friend Dr. Erin McFeely, a New Jersey-based pediatrician and co-author of the case report, to review the autopsy report. That review raised a question as to whether alpha-gal syndrome might be an explanation, and they got in touch with experts at the University of Virginia (UVA) School of Medicine in Charlottesville to review the case further.

An analysis of the man's blood revealed he carried antibodies against alpha-gal, as well as extremely high levels of tryptase, an enzyme released by immune cells into the bloodstream during allergic reactions. The UVA team asked the man's wife if he'd recently been bitten by ticks, and she noted he hadn't been bitten by ticks in the past year but had been bitten by chiggers.

Chiggers are a species of mite, not a type of tick, but the study authors noted that people sometimes think they've been bitten by chiggers when they've actually been bitten by the larvae of lone star ticks (Amblyomma americanum). Multiple tick species can spread alpha-gal syndrome, but the lone star tick is the most frequent culprit in the U.S.

Notably, white-tailed deer (Odocoileus virginianus) are a key host for these ticks. As the deer population has been exploding in New Jersey, the report authors flagged this as one factor driving up tick populations.

"The significance of this case is that a large and increasing population of the United States is being exposed to the Lone Star tick, both because the tick is moving north and because there are now large populations of deer in many states," they wrote. They added that the particular symptoms of an alpha-gal reaction might not alert patients to the fact it's an allergic reaction, and that could delay much-needed medical care.

"Even though the first episode scared the patient, neither he nor his wife considered it to be 'anaphylaxis,' and therefore, they did not connect the pain with the beef eaten 4 hours earlier," they wrote. "Thus, he had no reason to avoid eating a hamburger 2 weeks later."

This article is for informational purposes only and is not meant to offer medical advice.

Imagine this: You're at your doctor's office with a sore throat. The nurse asks, "Any allergies?" And without hesitation you reply, "Penicillin." It's something you've said for years — maybe since childhood, maybe because a parent told you so. The nurse nods, makes a note and moves on.

But here's the kicker: There's a good chance you're not actually allergic to penicillin. About 10% to 20% of Americans report that they have a penicillin allergy, yet fewer than 1% actually do.

I'm a clinical associate professor of pharmacy specializing in infectious disease. I study antibiotics and drug allergies, including ways to determine whether people have penicillin allergies.

I know from my research that incorrectly being labeled as allergic to penicillin can prevent you from getting the most appropriate, safest treatment for an infection. It can also put you at an increased risk of antimicrobial resistance, which is when an antibiotic no longer works against bacteria.

The good news? It's gotten a lot easier in recent years to pin down the truth of the matter. More and more clinicians now recognize that many penicillin allergy labels are incorrect — and there are safe, simple ways to find out your actual allergy status.

A steadfast lifesaver

Penicillin, the first antibiotic drug, was discovered in 1928 when a physician named Alexander Fleming extracted it from a type of mold called penicillium. It became widely used to treat infections in the 1940s. Penicillin and closely related antibiotics such as amoxicillin and amoxicillin/clavulanate, which goes by the brand name Augmentin, are frequently prescribed to treat common infections such as ear infections, strep throat, urinary tract infections, pneumonia and dental infections.

Related: Mold that led to penicillin discovery revived to fight superbugs

Penicillin antibiotics are a class of narrow-spectrum antibiotics, which means they target specific types of bacteria. People who report having a penicillin allergy are more likely to receive broad-spectrum antibiotics. Broad-spectrum antibiotics kill many types of bacteria, including helpful ones, making it easier for resistant bacteria to survive and spread. This overuse speeds up the development of antibiotic resistance. Broad-spectrum antibiotics can also be less effective and are often costlier.

Why the mismatch?

People often get labeled as allergic to antibiotics as children when they have a reaction such as a rash after taking one. But skin rashes frequently occur alongside infections in childhood, with many viruses and infections actually causing rashes. If a child is taking an antibiotic at the time, they may be labeled as allergic even though the rash may have been caused by the illness itself.

Some side effects such as nausea, diarrhea or headaches can happen with antibiotics, but they don't always mean you are allergic. These common reactions usually go away on their own or can be managed. A doctor or pharmacist can talk to you about ways to reduce these side effects.

People also often assume penicillin allergies run in families, but having a relative with an allergy doesn't mean you're allergic — it's not hereditary.

Finally, about 80% of patients with a true penicillin allergy will lose the allergy after about 10 years. That means even if you used to be allergic to this antibiotic, you might not be anymore, depending on the timing of your reaction.

Why does it matter if I have a penicillin allergy?

Believing you're allergic to penicillin when you're not can negatively affect your health. For one thing, you are more likely to receive stronger, broad-spectrum antibiotics that aren't always the best fit and can have more side effects. You may also be more likely to get an infection after surgery and to spend longer in the hospital when hospitalized for an infection. What's more, your medical bills could end up higher due to using more expensive drugs.

Penicillin and its close cousins are often the best tools doctors have to treat many infections. If you're not truly allergic, figuring that out can open the door to safer, more effective and more affordable treatment options.

How can I tell if I am really allergic to penicillin?

Start by talking to a health care professional such as a doctor or pharmacist. Allergy symptoms can range from a mild, self-limiting rash to severe facial swelling and trouble breathing. A health care professional may ask you several questions about your allergies, such as what happened, how soon after starting the antibiotic did the reaction occur, whether treatment was needed, and whether you've taken similar medications since then.

These questions can help distinguish between a true allergy and a nonallergic reaction. In many cases, this interview is enough to determine you aren't allergic. But sometimes, further testing may be recommended.

One way to find out whether you're really allergic to penicillin is through penicillin skin testing, which includes tiny skin pricks and small injections under the skin. These tests use components related to penicillin to safely check for a true allergy. If skin testing doesn't cause a reaction, the next step is usually to take a small dose of amoxicillin while being monitored at your doctor's office, just to be sure it's safe.

A study published in 2023 showed that in many cases, skipping the skin test and going straight to the small test dose can also be a safe way to check for a true allergy. In this method, patients take a low dose of amoxicillin and are observed for about 30 minutes to see whether any reaction occurs.

With the right questions, testing and expertise, many people can safely reclaim penicillin as an option for treating common infections.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Clouds of pollen floating over the mammoth steppe at the end of the last ice age may have helped drive woolly mammoths to extinction, a new study claims.

Researchers say a boom in vegetation due to global warming may have released so much pollen, it triggered allergic reactions in animals — blocking their sense of smell and preventing them from communicating normally with one another. The inability to sniff each other out during the breeding season would have prevented mammoths from finding sex, the team argue, leading to a precipitous drop in population size and, eventually, extinction.

"One of the possible mechanisms for the extinction of animals during climate change could be a violation of the sense of smell due to the development of allergies when the flora changes," the researchers wrote in the study, which was published Aug. 27 in the journal Earth History and Biodiversity. "The purpose of this work is to propose a new evolutionary mechanism for the extinction of mammoths and other animals based on the disruption of communication."

Woolly mammoths (Mammuthus primigenius) lived during the Pleistocene epoch (2.6 million to 11,700 years ago). They disappeared across much of their range around 10,000 years ago, although a small population survived on Wrangel Island — a remote island off northeastern Russia — until 4,000 years ago. Researchers think a combination of inbreeding, hunting by humans and major changes in vegetation all pushed mammoths to extinction, but there is ongoing debate about how much each of these factors contributed to their demise.

Related: 'Closer than people think': Woolly mammoth 'de-extinction' is nearing reality — and we have no idea what happens next

Allergies would have disturbed several vital functions of mammoth life, the researchers argue. Animals use their sense of smell to find food and mates, to navigate during migration and to evade predators, so the mammoths' stuffed-up trunks may have doomed them, the researchers wrote in the paper.

One way to test if mammoths suffered from allergies is to examine their stomach content for plants and pollen that trigger allergies, the authors of the new study suggest. Some carcasses also have pollen embedded in the mummified tissues or preserved plant material around them that could help identify past irritants, according to the study.

Next, to determine whether these chemicals actually triggered an allergic reaction in mammoths, the researchers suggest looking for the immune system proteins the body produces during an allergic response. One of the main ones is immunoglobulin E (IgE), which is produced in the intestine and then pooped out, so testing fossilized mammoth feces, or coprolites, could be a way to see if the mammoths had bad cases of hay fever. So far, no published research has looked for traces of IgE in ancient mammal samples, according to the study.

One expert isn't convinced that allergies played a big part in the downfall of mammoths. "This idea seems pretty far out there and I'm not sure how you would ever prove it," Vincent Lynch, an evolutionary biologist and associate professor at the University at Buffalo in New York, told Live Science in an email.

Ancient DNA samples do indicate that the last-surviving woolly mammoths lost the ability to smell certain plants, Lynch said. The reconstructed genome of a mammoth from Wrangel Island showed mutations in genes associated with the ability to detect floral scents, suggesting the last mammoths couldn't smell flowering plants.

However, until the authors' idea is experimentally tested and supported by further research, Lynch said he still thinks a combination of environmental factors and human impacts caused mammoths to die out.

Some people just can't stop scratching after they're bitten by a mosquito — but not everyone gets itchy after a bug bite or similar allergy-triggering encounter. Now, new research in mice pinpoints differences in immune system activity that may determine whether you end up itchy.

The skin is densely populated with sensory neurons, which are nerve cells that detect changes in the environment and then trigger sensations, such as pain, in response. When a person encounters a potential allergen, like mosquito saliva, these neurons detect it and may trigger an itchy sensation in response. They also help activate nearby immune cells, which kick off an inflammatory reaction featuring swelling and redness.

Some people who are repeatedly exposed to an allergen can develop chronic allergic inflammation, which fundamentally changes the tissues where that inflammation is raging. For instance, the immune cells that respond to allergens can change the nerves' sensitivity, making them more or less likely to react to a substance.

"We all have sensory neurons, so we can all feel itchy — but not all of us get allergies, even though we're surrounded by the same allergens," senior study author Dr. Caroline Sokol, a professor of allergy and immunology at Harvard Medical School and Massachusetts General Hospital, told Live Science. "So what defines whose sensory neurons fire in response to allergens and whose don't?"

Related: Could allergies be 'deleted' someday?

To find out, Sokol and colleagues exposed mice to a chemical called papain, which causes an itchy sensation that makes mice scratch their skin. The different groups of lab mice in the study were missing different immune cells. The research, published Wednesday (Sept. 4) in the journal Nature, found that mice that lacked a specific type of T cell didn't scratch when they were exposed to papain.

The researchers wanted to find out how these cells, dubbed GD3 cells, drove sensory nerve responses. They grew GD3 cells in the lab and treated them with a chemical to make them release signaling molecules called cytokines. Then, they injected mice with normal immune systems with the cytokine-containing liquid the cells were grown in.

This treatment didn't trigger itchiness on its own. However, it did intensify the mice's scratching responses to a variety of allergens, including mosquito spit. This suggested that something released by GD3 cells hiked up the nerve-induced itching.

By comparing the chemicals secreted by GD3 cells with those from other immune cells in the central layer of the skin, the researchers discovered that only one factor was unique to the GD3 cells: interleukin 3 (IL-3), which is known to help regulate inflammation.

Only some sensory neurons responded to IL-3. Those that did respond became more likely to trigger an itch — a sign that the cytokine "primes" neurons to react to allergens.

In contrast, when the researchers removed the genes for IL-3 or its receptors — or removed the GD3 cells entirely — the mice could not initiate an allergic response. With further experiments, the researchers concluded that IL-3 activates two separate signals: one that promotes the nerve-driven itching and another that controls the immune side of the allergic response.

By releasing IL-3, the GD3 cells were "absolutely essential" for setting the threshold at which a sensory nerve would react to an allergen, Sokol said. This chain reaction involving IL-3 "may give us a new pathway to treat patients with chronic itch disorders," she added.

However, so far, the research has been conducted only in mice, so the researchers can't be certain that human cells will behave the exact same way. Although the mouse immune cells in the study have very similar genes and proteins as their human equivalents, Sokol emphasized that it's important to understand whether and how human T cells react to IL-3. That data is needed to translate the finding into itch treatments or ways to predict who might be at risk of allergies.

"We all have that friend who doesn't react to mosquito bites and the friend who looks horrific after a day outside," Sokol said. "We believe [the IL-3 pathway] is determining that in real time, because when we look at mosquito bite-induced itch — and the allergic immune response that follows — we see that it is completely dependent on the cells in this pathway."

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The Food and Drug Administration (FDA) has approved the first needle-free treatment for the life-threatening allergic reaction anaphylaxis.

In a statement released Friday (Aug. 9), the FDA announced it had approved Neffy, a nasal-spray formulation of epinephrine. That's the same medication found in EpiPens.

Also known as adrenaline, epinephrine is a chemical made by the body that plays a role in its fight-or-flight response. Epinephrine treats allergic reactions because it rapidly relaxes the muscles of the airways, preventing spasms and opening up passageways needed for breathing. In addition, it helps reverse a dangerous drop in blood pressure that can be triggered by severe allergies in part by constricting blood vessels.

These dangerous effects unfold during anaphylaxis, a sudden and life-threatening allergic reaction that affect the whole body. And now, there will be a needle-free option to treat the condition.

Related: Could allergies be 'deleted' someday?

"Today's approval provides the first epinephrine product for the treatment of anaphylaxis that is not administered by injection," Dr. Kelly Stone, the associate director of the Division of Pulmonology, Allergy and Critical Care in the FDA's Center for Drug Evaluation and Research, said in the statement.

"The availability of epinephrine nasal spray may reduce barriers to rapid treatment of anaphylaxis," Stone said. "As a result, neffy provides an important treatment option and addresses an unmet need."

Neffy is approved for adult and pediatric patients who weigh at least 66 pounds (30 kilograms). It's a single-dose spray intended to be administered into one nostril. Similar to products like EpiPens, a second dose of the spray can be given if a person's symptoms do not improve. The second dose would require a second Neffy spray bottle and it would be given in the opposite nostril as the first dose.

"Patients may need to seek emergency medical assistance for close monitoring of the anaphylactic episode and in the event further treatment is required," the FDA notes.

Some medical conditions, including a history of nasal surgery, may affect how well Neffy absorbs through the tissues of the nose. Because of that, the FDA says individuals with such medical histories should talk to a health care provider before using Neffy.

This article is for informational purposes only and is not meant to offer medical advice.

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As a child, you may have been told that playing outside in the dirt is good for you because it strengthens your immune system. But is there any evidence to back this claim? 

In short, yes — several studies suggest that early exposure to dirt may reduce kids' risk of developing allergies and autoimmune conditions. In other words, it may guard against conditions in which the immune system unhelpfully reacts to allergens or to the body's tissues.

As a child's immune system develops in the early years of life, the army of protective cells within the body have to learn how to distinguish between the body's own cells and foreign substances that are either harmless or disease-causing, such as bacteria and viruses. It must learn to spot the disease-causing pathogens in order to attack them. 

Related: What do some allergies last a lifetime? Newly described immune cells to blame

It turns out that the molecular signals that drive the expansion of this regulatory arm of the immune system mainly come from microbes in the gut, Graham Rook, a professor emeritus of medical microbiology at University College London, told Live Science. This collection of microbes is called the "gut microbiome" and is essential to our health. For instance, some of these microbes help produce vitamins that we need to live, and they help us digest our food. 

The first year of life is crucial to the microbiome's development. Babies receive bacteria as they pass through the birth canal, if they're born vaginally, and from milk if they're breastfed. As children grow, they are steadily exposed to microbes from a wide array of sources. 

A theory called the "old-friends hypothesis" suggests that, the greater the range of microbes we're exposed to in early childhood, the more diverse our microbiomes will be and thus the better our immune systems will recognize friend from foe. The term "old friends" refers to helpful, or "commensal," microbes that live on and in the body without harming a person's health.

This theory, proposed by Rook in 2003, is similar to the more widely known hygiene hypothesis, which suggests that a lack of early exposure to germs makes people more prone to immune conditions. Multiple studies, for instance, have demonstrated a link between growing up on a farm or in a household with pets and having a lower likelihood of children developing allergies, compared with kids in urban or pet-less environments. 

However, the old friends hypothesis stresses the importance of being exposed to commensal microbes in early life, as opposed to infectious pathogens. This idea is backed by research: several studies in Europe suggest early exposure to germs does not guard against the development of allergies. Another critique of the hygiene hypothesis is that it downplays the importance of good hygiene to preventing disease, pushing the idea we've become "too clean," Rook and colleagues argued in a 2016 review. 

The old friends hypothesis, on the other hand, could help explain why antibiotic overuse in early life, which can wipe out much of the gut microbiome, and cesarean deliveries, which don't expose newborns to vaginal bacteria, have been tied to an increased risk of allergies. 

A trial in Finland looked at whether city kids' immune systems could be bolstered with grass and soil that had been taken from the forest floor. They found that, within a month, children who played in the dirt had a more diverse collection of harmless bacteria on their skin and more immune-regulatory cells and signaling molecules in their blood than those who played on gravel playgrounds. This hints that exposure to bacteria within dirt could help the immune system mature, theoretically reducing the chances of it becoming overactive. 

Similarly, a Swedish study published in 2024 found that children who either grew up on dairy farms or had pets had lower rates of allergies than those who didn't. They also had more harmless bacteria in their guts, so the study authors concluded that the two phenomena may be linked.

While the microbiome is important, there are many other factors that affect someone's risk of developing allergies, including their genetics, Dr. Robert Wood, a professor of pediatrics at Johns Hopkins Medicine in Baltimore, told Live Science. As a general message, though, children should be encouraged to go outside and play in the dirt, he said. 

However, scientists' current understanding of risk factors for immune conditions can't always be translated into practical advice. For instance, if you have a dog, you may have a somewhat lower chance of developing allergies than a pet-less person — but you can't tell somebody to get a dog as a guaranteed way to prevent allergies, Wood said.

Dirt in heavily polluted areas can also be unhealthy for kids, as it could contain harmful contaminants, he noted. This clearly wouldn't be the sort of dirt that you'd want your child to be exposed to. And because dirt can contain potentially harmful chemicals, such as lead, as well as parasites, care should be taken to stop children from inhaling or eating it.

Editor's note: This article was updated on Nov. 28, 2024 to include information about the Swedish study. The article was originally published on April 2, 2024.

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People with severe allergies to foods like milk, peanuts and shellfish will have a new way to ward off dangerous reactions after accidental exposure to the foods.

A drug called Xolair (generic name omalizumab) has just been approved for the treatment of multiple severe food allergies, the U.S. Food and Drug Administration (FDA) announced Friday (Feb. 16). The injectable drug is a monoclonal antibody, meaning it contains lab-made proteins that latch on to a specific target in the body. Once inside a person, Xolair grabs hold of immunoglobulin E (IgE), the type of body-made antibody primarily responsible for allergic reactions.

Many food allergies are driven by IgE, including those to milk, eggs, soy, peanuts, tree nuts, fish, shellfish and wheat. (IgE-driven wheat allergy is different from celiac disease, an autoimmune condition driven by other elements of the immune system.)  

Xolair was previously approved to treat other conditions, including allergic asthma, but its newest approval means it can now be used to guard against allergic reactions caused by multiple food triggers.

"This newly approved use for Xolair will provide a treatment option to reduce the risk of harmful allergic reactions among certain patients with IgE-mediated food allergies," Dr. Kelly Stone, associate director of the Division of Pulmonology, Allergy, and Critical Care in the FDA's Center for Drug Evaluation and Research, said in Friday's statement.

Related: What do some allergies last a lifetime? Newly described immune cells to blame

"While it will not eliminate food allergies or allow patients to consume food allergens freely, its repeated use will help reduce the health impact if accidental exposure occurs," Stone said.

Importantly, Xolair is not a replacement for epinephrine injections — namely, EpiPen devices, which are used to reverse a life-threatening, body-wide allergic reaction called anaphylaxis. The EpiPen injection keeps a person's airways open and blood pressure stabilized in the event they have exposure to an allergen and have this dangerous reaction.

Xolair, by contrast, is injected every two to four weeks as a preventive measure to help people build tolerance to allergens and thus reduce the severity of their allergic reactions if they are exposed.

The recommended dosage and timing of a person's Xolair injections vary depending on their body weight and the amount of IgE in their blood, according to the drug's distributor, Genentech. The injections can be given by a health care provider or at home through self-injection, if a clinician deems that method appropriate for the patient.

Xolair was tested in a trial that included nearly 170 adolescents and children at least 1 year old, as well as three adults, according to trial details published Feb. 25 in the New England Journal of Medicine (NEJM). All of the participants were allergic to peanuts and at least two additional foods; these allergies were confirmed with various tests, including a skin-prick test and IgE test. The participants received either Xolair or a placebo for four to five months.

The researchers found that 68% of those who received Xolair were able to consume a dose of peanut protein without moderate to severe symptoms, such as whole-body hives or vomiting. That's compared with only 6% of the placebo group. The researchers also saw similar rates of improvement when it came to people's reactions to cashews, milk and eggs.

In the NEJM report, the scientists noted that the observed levels of protection "are likely to exceed those that would be needed for the amounts of food that are typically encountered during accidental exposure." 

That said, a significant percentage of people who took Xolair — 17% — saw no change in their peanut tolerance over time. "As a result, continuation of strict allergen avoidance is still necessary, despite treatment with Xolair," the FDA cautioned.

Additional studies will be needed to fully understand the reasons for treatment failures, as well as whether the therapy could actually help treat the core cause of people's allergies if used regularly and shortly after diagnosis, the NEJM report notes. 

The most common side effects of the injection were fever and reactions at the injection site. The drug's label also warns of potential fevers, joint pain, rashes and parasitic worm infections. (IgE is thought to be key to fighting off parasites, so blocking the antibodies might raise the risk of such infections.)

In addition, the FDA emphasized that people should initially receive Xolair in a health care setting, as there have been some reported cases of patients experiencing anaphylaxis shortly after the drug's administration.

Xolair was previously prescribed "off-label" for food allergies but should now be easier to access for the purpose, The Associated Press reported. The list price typically runs $2,900 a month for children to $5,000 a month for adults, but insured patients generally pay less out of pocket.

Editor's note: This article was updated on Feb. 26, 2024 to add information from a newly published New England Journal of Medicine paper. The story was first published on Feb. 20. 

This article is for informational purposes only and is not meant to offer medical advice.

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Warm weather will soon grace the U.S., replacing the short, cold days of winter — but it will also usher in an onslaught of seasonal spring allergies. Could there come a day when allergies are a thing of the past?

Remarkably, on that front, there is a glimmer of hope.

Scientists recently came a step closer to finally explaining why some allergies can last a lifetime while others fade. Turns out, the persistence of allergies may be linked to a unique type of immune cell — and someday, by modifying or deleting these cells, scientists could theoretically help make people's allergies less cumbersome or even cure them. 

Allergies have long puzzled scientists — researchers don't fully understand why allergies affect some people but not others, or why allergies emerge in the first place. Previous research has found that the type of antibody most often associated with allergies is produced by cells that don't last very long in the body, which makes people's lifelong allergies harder to explain. 

Two recent studies, published back-to-back in the journal Science Translational Medicine, might help solve that mystery. The studies, one of which examined children with allergies and the other adults, described a unique type of immune cell that hasn't been tied to allergies before.  

Related: Best air purifiers for allergies 2024 

The cells typically produce a type of antibody not associated with allergies, called immunoglobulin G (IgG). But a subset of these cells actually switch over to making an allergy-related antibody called immunoglobulin E (IgE) when confronted with an allergen, whether pollen, pet dander or peanuts.

IgE is usually produced by short-lived plasma cells, which churn out antibodies as an immediate and temporary line of defense for the body. These antibodies are thought to help fight off parasites, for instance, but in allergies, they go after harmless proteins instead.

The newly described cells are a type of memory B cell, which typically remember viruses and bacteria and spit out IgG when those invaders show up. But now, scientists have uncovered a subset of memory B cells that remember allergens and can make IgE. These cells are not short-lived like plasma cells and instead linger in the body for an indefinite amount of time — many years, or possibly a person's entire life.

The new research could be helpful in developing new treatments or tests for allergies — for instance, to assess if a childhood allergy is likely to persist into adulthood, the study researchers say. 

"These cells may be analyzed as sort of a [biological marker] for risk of allergy or allergy persistence," said Maria Curotto De Lafaille, a professor of pediatrics and of immunology and allergy at the Icahn School of Medicine at Mount Sinai Hospital in New York and senior author of the study on children.

That study focused on children with peanut allergies and analyzed blood samples from 58 kids who are allergic to peanuts and 13 who aren't. The second study analyzed a smaller number of blood samples from adults with a variety of allergies, including six with a birch-pollen allergy, four with a dust-mite allergy and 11 with peanut allergies.

While all the children with allergies avoided eating peanuts, participants in the adult study with birch-pollen allergies gave blood samples before and after starting an immunotherapy treatment for their allergies. This treatment is designed to desensitize the immune system by exposing patients to a small amount of allergen and then gradually increasing the dose over time. 

Both studies looked for signs that memory B cells might switch over to producing IgE after being exposed to allergens. For instance, researchers examining samples from children searched for B memory cells with a specific type of receptor, or part of the antibody that enables it to bind to specific proteins. This receptor is more common in people with eczema and asthma, two inflammatory conditions that often coincide with allergies, than in people without the conditions.

Related: Inflammation is a 'mismatch between our evolutionary history and modern environment,' says immunologist Ruslan Medzhitov

The two studies pinpointed the same type of memory B cell in people with allergies, although notably, earlier research had found similar cells in animals and in people with asthma and eczema. 

The cells "directly create IgE antibodies, the type that make us allergic," Joshua Koenig, an assistant professor of medicine at McMaster University in Canada and the first author of the paper focused on adults, told Live Science in an email. "They're really the long-term memory reservoir of allergy." 

The research is part of "an important area of study, and the key to understanding the persistence of diseases that are caused by antibodies, like allergies," Dr. Sarita Patil, an assistant professor of allergy and immunology at Harvard Medical School who was not involved in the studies, told Live Science in an email.

Both studies were limited by having a small number of participants. Future research could look at how immunotherapy for peanut allergies impacts the newly described cells and the antibodies that they release. It's known that the immunotherapy reduces people's allergen-specific IgE levels over time, but the impact on these memory B cells is unclear. 

Other future research could see whether the behavior of these cells changes over time, especially in children, who sometimes outgrow their allergies.

Understanding why allergies persist could one day help scientists eliminate or modify these allergy-specific cells so that they don't produce IgE and trigger an immune response anymore, Lafaille said. In other words, studies building on this research might one day help lessen the impact of allergies or even cure them.

Editor's note: This story was updated on April 12, 2024. It was first published on Feb. 16, 2024. 

This article is for informational purposes only and is not meant to offer medical advice.

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Allergies are common in people, and they can often accompany animal contact, triggering symptoms such as itchy eyes and sneezing.

But do allergies work the other way around? Can dogs and cats be allergic to us?

According to Dr. Heather Edginton, an assistant clinical professor of dermatology at the Cornell University College of Veterinary Medicine, our furry friends can have allergic reactions to people.

"The three main categories of allergies we see in dogs [and cats] are flea allergies, food allergies and environmental allergies," Edginton told Live Science. "An allergy to humans would fall in the category of environmental allergies."

Fortunately for many pets and animal lovers, allergy symptoms in pets are typically mild. Only very rarely are the symptoms dangerous or life-threatening. The most extreme allergic reaction animals (and humans) can experience is an anaphylactic reaction, Edginton said, which involves swelling, vomiting, seizures and even death in dogs and cats, according to the Merck Veterinary Manual. However, these severe reactions in pets are typically brought on by food allergies or bee stings, not by contact with humans.

Related: Do bees really die if they sting you?

Typically, when a dog or a cat is allergic to humans, its reaction is similar to the way a human who is allergic to dogs or cats might react. Usually, a dog or cat that is experiencing an allergic reaction will scratch repeatedly at otherwise healthy-looking skin. This condition is called atopic dermatitis, more commonly known as eczema. In felines and canines, eczema can be brought on by human dander, which includes dead skin cells and hair. Pets that are allergic to human dander and share indoor spaces with people will encounter it everywhere, including from carpets and vents.

And it turns out that, for pets with allergies, an allergy to humans is typically included. Of the roughly 20% of dogs that have symptoms of allergies, about half exhibit allergies to human dander. And while atopic dermatitis is common in cats, less is known about how frequently it is caused by human contact.

"When we do allergy testing [in dogs or cats], we find that they are usually allergic to 12 or more things at a time, and humans are often just one of those things," Edginton said. Other environmental allergies found in dogs include dust, pollen and mold spores, according to the review.

For pups with human allergies, there are several treatment options, such as administering preventative antihistamines, according to Edginton. This is often given as a pill and means the animal will need daily doses of the drug to stave off symptoms.

But not all pets respond to the drug.

"Ultimately, antihistamines only tend to be effective about 30% of the time," Edginton said. In 2015, Edginton and colleagues published a study on the effectiveness of the antihistamine loratadine, commonly known as Claritin, on 27 cats with skin allergies and found that the drug was generally ineffective.

Another treatment option is giving pets oral steroids such as prednisone.; According to the International Committee on Allergic Diseases of Animals, oral steroids in dogs tend to be more effective than antihistamines in treating acute allergic flare-ups as they happen, and they can also be used long-term therapeutically. However, side effects include lethargy, increased panting and increased hunger. Similar side effects are seen in cats.

A third option is allergen-specific immunotherapy, or allergy shots, according to the Merck Veterinary Manual, which involves injecting a pet that has allergies with controlled amounts of allergens to dampen the allergic reaction through exposure. This technique is effective in dogs 60% of the time, according to Edginton, and as much as 78% effective in cats.

Ultimately, allergies to humans can be treated but they can't be cured. "That's the thing with allergies in dogs," Edginton said. "Therapy is forever. Once you stop, the allergies will come back."

This article is for informational purposes only, and is not meant to offer medical advice.

Basking in the sun can cause a number of health conditions, from sunburn to skin cancer. But can you be allergic to the sun, too?

The short answer is, yes, you can have an allergic reaction to ultraviolet light from the sun. A sun allergy produces an itchy rash that may present as red bumps, red patches, blisters or hives on the sun-exposed areas of the skin, Dr. Debra Jaliman, a board-certified dermatologist based in New York and a member of the American Academy of Dermatology, told Live Science.

However, the term "sun allergy" is an umbrella term that encompasses several immune responses to ultraviolet light. Some sun allergies may be linked to a person's genetic make-up, while others can develop in response to certain chemicals from medicines or cosmetics, according to Harvard Health.

Related: What causes allergies?

Polymorphic light eruption (PMLE) is one of the most common forms of sun allergy. PMLE may affect 1 in 10 people worldwide, but it tends to be more prevalent in the Northern Hemisphere, according to a 2022 meta-analysis published in the Journal of the European Academy of Dermatology & Venereology. PMLE usually manifests as a rash that appears within two hours of sun exposure. This condition typically affects more women than men, and its symptoms often begin in early adulthood. Scientists don't know what causes PMLE, according to the medical resource StatPearls.

In rare cases, PMLE may be hereditary. This form of sun allergy, called Actinic prurigo, predominantly affects Native American populations in the northern, southern and central U.S. The symptoms of Actinic prurigo often begin earlier — and are more severe — than in typical PMLE, Harvard Health noted.

Another common form of sun allergy is photoallergic eruption, a skin reaction triggered by an interaction between sunlight and chemicals either ingested or applied to the skin. This blistery rash may take one to two days to develop and can spread to areas of the skin that were not exposed to the sun, according to Harvard Health. Photoallergic eruption "can occur in people of all skin types, but light-skinned individuals who are more sensitive to the sun are more likely to get the symptoms," Jaliman said.

Photoallergic eruption is often caused by synthetic chemicals found in topical cosmetics, including musk fragrances and benzophenones, an ingredient in some mineral sunscreens. But natural substances, such as lime juice, can trigger it too, she said. A number of prescription medications, including "certain antibiotics, such as tetracycline and ciprofloxacin; sulfur-based drugs, like hydrochlorothiazide [a diuretic]; and isotretinoin, a medication used to treat acne," can also cause photoallergic eruption, Jaliman noted.

Solar urticaria is another form of sun allergy, although most doctors consider this condition rare, according to Harvard Health. People with solar urticaria tend to develop hives and bumps on the skin immediately after being exposed to sunlight. It is not known what causes this condition, according to StatPearls.

Jaliman emphasized that anyone can develop a sun allergy, even if they have never had an adverse reaction to ultraviolet radiation. "For example, you could take a certain antibiotic for years, but then one day develop a photoallergic reaction to it," she said. "Unfortunately, [these] allergic reactions can develop over time."

This article is for informational purposes only and is not meant to offer medical advice.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website! 

"Inflammation is the new evil. Let me explain."

"You might think inflammation isn't really THAT big of a deal…but trust me when I say it is." 

Scan social media and you'll easily find content that portrays inflammation as a villain. 

In every bookstore you'll find at least one anti-inflammatory diet recipe book, and in your local drug store, an array of products parading their magical anti-inflammatory ingredients. 

But inflammation has evolved over millennia to protect us, says Ruslan Medzhitov, a Sterling Professor of Immunobiology at Yale University School of Medicine and Investigator at the Howard Hughes Medical Institute in Maryland who studies inflammation in the context of autoimmune disease and allergies. 

Related: 'If you don't have inflammation, then you'll die': How scientists are reprogramming the body's natural superpower

So if not all inflammation is bad for us, how do we know the difference between "good" and "bad?" 

Live Science spoke with Medzhitov about how inflammation is the body's response to a system out of equilibrium, how chronic inflammation results from a mismatch between our evolutionary environment and the modern one, and whether there's any evidence for specific "anti-inflammatory" diets.

Emily Cooke: What is inflammation?

Ruslan Medzhitov: Inflammation is an essential part of our defense system. It evolved to protect us from a variety of challenges, including many challenges that come from the outside world, such as infection or injury or toxins. Without inflammation, we would quickly succumb to infections and die and that would be the end of it. 

Mostly what we know about inflammation is what happens at the extreme, when there is an infection or injury and then there is swelling and redness and fever and things like that. But inflammation plays an important role in a variety of settings, including when we don't diagnose it clinically as inflammation, including when we may not even feel it, it's asymptomatic. 

Under the hood, it plays an important role in coordinating metabolism, different physiological functions and so forth. Those functions of inflammation are much, much less appreciated and much less studied. And just to give one quick example of the reach of inflammation throughout biology is that it controls our metabolism, controls adaptation to the environment in terms of thermogenesis [heat production] and [even controls] aspects of behavior. And that last part is what's particularly interesting, where inflammation can for example, control mood. It can control avoidance behaviors, and anxiety behaviors. And these are all presumably by design, meaning that these are meant to be protective phenomena, they're beneficial in certain settings. When this response becomes dysregulated in some way, it can lead to particular types of pathologies and disorders and so forth that inflammation unfortunately is more famous for. 

Related: Brain inflammation may drive mood changes in Alzheimer's

EC: Is there such a thing as "good" and "bad" inflammation?

RM: Yes, and there are two ways to divide between good and bad inflammation. 

So, good inflammation operates within the normal range. What is "normal" is decided not by us, by how we feel. It is decided by millions of years of evolution and calibrated by, on average, if you have this type of response, on average you have a better chance for survival. But that was in a very, very different setting. Throughout our evolutionary history, of course, our environment was very different. But the genes that evolved under those conditions, we still have them and they still operate as if nothing [has changed], because dramatic change in the environment happened only very recently. 

Good inflammation will be the one that operates with the right magnitude, that provides maximum benefit and lowest possible cost. 

But that line is very fuzzy and one can shift into what would be now called "bad" inflammation, which is a protective response but in overdrive. 

Phenomena like cytokine storms [when chemical signals associated with inflammation go haywire], sepsis [an over-reaction to infection], anaphylactic shock [a severe allergic reaction], these are all examples of inflammation that went way too far in magnitude, so it's induced too strongly. 

Again, what is a good magnitude versus too much? The logic of it is decided by evolution. 

So one delineation of good inflammation [versus] bad inflammation is just the magnitude of the response. 

The second type is when inflammation may be induced in the right magnitude, but it's induced for the wrong reasons. And that is what often leads to chronic inflammation. But the reason that happens is, again, in large part, a mismatch between our evolutionary history and modern environment. [Being obese was uncommon in our evolutionary past], because that would be unheard of under normal, natural conditions where you have to walk for 10 miles to find something to eat every day. 

In the modern environment, obesity is common. But that's not what our genes evolved to deal with and they misinterpret it, induce inflammation and then obesity-associated inflammation then becomes a problem. 

And the second example of that is aging-associated inflammation. Most of our ancestors throughout history would be dead by 30 years of age. Therefore the body is not, sort of, designed to deal with changes that happen at an advanced age. Many age-related deteriorations in body functions can be interpreted by inflammation as, "oh, something is off, I'm supposed to get in action when something gets off a normal homeostatic [self-regulating] range." And what happens then? It creates this vicious cycle where, [in response to] these deviations that are age-related or obesity-related or [related to] other evolutionarily-new and modern aspects of our lifestyle, inflammation is induced. [The body is] thinking "I will try to fix it." But there's nothing to fix. And that's what is, really, mostly bad inflammation. 

Related: DNA-damaging gut bacteria may fuel colon cancer in patients with inflammatory bowel disease

EC: Is it possible to modulate "bad" inflammation with lifestyle changes, for example with anti-inflammatory diets? Is the evidence actually there? 

RM: Yes, it is possible to modulate it.  But if you look at the common denominator —  so exercise, diet, healthy food, diverse food, avoid processed foods, avoid sedentary lifestyle, have enough sleep, reduce stress — if you think about what is the common denominator, all of them have one thing in common: modify your lifestyle to approximate, slightly better, the way we evolved to be. 

EC: From an immunobiology perspective, what message would you want people to know if they were concerned about inflammation? 

RM: Well, I would say that inflammation in general is something that we all need to protect ourselves. We don't want to completely eliminate it, that would be lethal basically. Without inflammation we cannot survive. That most causes of unwanted or "bad" inflammation in the modern world, in industrialized countries at least, have to do with aspects of our lifestyles that are unnatural and unhealthy. And I think diet and physical activity are probably the major drivers. 

I mean, this is not anything new. 

But having said that, there are also conditions that are truly pathological, like autoimmune diseases, for example, or sepsis, and that's where inflammation is mostly evil and mostly just needs to be knocked down and controlled. 

But for the majority of people this has to do with chronic inflammation that may be even asymptomatic, sub-clinical, but under the hood slowly contributes to various sorts of unhealthy conditions. And that's where the steps of simple interventions of having the right diet and the right physical activity [come in.]

And I would just add one more thing. Nobody knows what the right diet actually is. I think it's a failure, both on the part of the scientists, and the part of communicators of science. Because if the science is not there, what do you communicate? 

And that's that we don't really understand food. We don't understand what a healthy diet is. We don't understand how it affects our bodies. We know some obvious things, trivial things, calories and things like that, vitamins. But beyond that our knowledge is really at the medieval level. 

And that, I think, is going to be the next big frontier in biomedical science. So when I say healthy food, healthy diet, I'm just saying it in sort of, in terms of the obvious aspects of it. Eating processed food, highly processed simple sugars, high calorie, unbalanced, those are things that are obviously bad. But beyond those trivial aspects, there is a lot more to it that we don't really understand. So, I say healthy diet, but with the qualification that we only know very little about what a healthy diet really is. 

Editor's Note: This interview has been condensed and edited for clarity.

From jewelry and kitchen utensils to door handles and hand tools, metals can be found in a variety of everyday items — and for some people, exposure to these objects can trigger an allergic reaction.

But what happens when you have a metal allergy?

The symptoms of a metal allergy can range from relatively benign to life-threatening, given that the allergy can, in rare cases, cause metal-containing surgical implants to fail, Dr. Santhosh Kumar, an allergist based at the Children's Hospital of Richmond at Virginia Commonwealth University, told Live Science by email.

However, the most common symptom of a metal allergy is contact dermatitis, an itchy, swollen skin rash caused by direct contact with an allergy-triggering substance, according to a 2012 review published in the journal Dermatology Research and Practice. Evidence suggests that these reactions are related to the fact that common metals that cause contact dermatitis — such as nickel, cobalt and chromium — lack a full set of electrons.

Related: What causes allergies?

Electrons in atoms orbit around a nucleus, and for an atom to be stable, it typically needs eight electrons whizzing around the orbital path that's farthest from the nucleus. But nickel, for example, has only two electrons there; shedding those two electrons stabilizes the atom and gives it a positive charge. Thus, the nickel in a necklace or a pants button can shed charged nickel atoms, known as ions, over time, and these interact with the wearer's skin.    

Specifically, the nickel ions latch on to specific proteins present in the skin. And because these metal-protein complexes are perceived by the body as "foreign," they trigger an immune response, according to the medical resource StatPearls. 

Through prolonged and repeated exposure to a metal, immune cells can become sensitized to it in this way — but it's not fully understood why some people experience this sensitization while others don't. The American Academy of Pediatrics (AAP) notes that genetic factors related to the immune system and to skin's outer barrier likely play a role. Environmental factors, such as whether you regularly work with potentially allergy-triggering metals, may also raise the risk, Mayo Clinic says.     

Symptoms of contact dermatitis can range from a localized flare-up to a whole-body rash, and the severity of the skin rash depends mainly on how much the skin barrier has been penetrated or damaged by the metal in question. In terms of appearance, metal-related contact dermatitis "does not look any different than many other rashes," and may closely resemble an eczema or poison-ivy rash, Kumar said. 

Dr. Raman Madan, a dermatologist based in New York and a fellow of the American Academy of Dermatology, described the look of a metal-allergy rash as "red, scaly, crusty or dark," with the affected area often being itchy, swollen and painful to the touch. The symptoms of contact dermatitis start appearing immediately after exposure, and if untreated, the rash can last anywhere from 12 hours to a month, he told Live Science by email. 

(The AAP also notes that symptoms can appear within just 30 minutes of metal exposure, but Mayo Clinic adds that they can sometimes take hours to days to show up.)

People with metal allergies can also develop systemic contact dermatitis, which occurs when metal particles reach the skin from the bloodstream, as can occur when these particles are ingested with food or medication. Systemic contact dermatitis can cause a widespread pink-to-red skin rash, papules (small, solid bumps on the skin), and exfoliative erythroderma, in which the skin becomes inflamed and starts peeling, according to the 2012 review.

People with metal allergies can also have reactions to certain surgical implants, according to a 2015 review published in The Journal of Allergy and Clinical Immunology.

Various heart pacemakers, intrauterine devices, artificial teeth and joint replacements are made using metal composites. Reactions to implants can result in localized pain, swelling and itching near the implant site, and chronic inflammation of the palms and soles. They can even cause a failure of the device, often due to harmful changes in the surrounding tissues.

These reactions can sometimes happen in patients with no prior history of metal allergy, the review authors noted, but in individuals previously diagnosed with a metal allergy, surgical implants can be modified to minimize the risk of a reaction.

Thankfully, allergic reactions to metal surgical implants are relatively rare, Kumar emphasized.

This article is for informational purposes only and is not meant to offer medical advice. 

An Arizona man has survived being attacked by a swarm of 1,000 "killer" bees, local news network Arizona's Family reported. 

John Fischer, 60, was out in his neighborhood in the town of Florence with his dog, Pippin, when the bees swarmed. While Pippin was able to run away, Fischer, who uses a wheelchair, was overcome by the swarm when his wheelchair tipped over. Fischer was treated at the hospital, where he was given morphine before having the stingers removed; he said his medical providers found more than 250 stingers in his body. Fischer has since been released from the hospital and is now recovering from the hundreds of stings to his arms, eyes, mouth, ears, legs and back. (Pippin reportedly sustained around 50 stings during the attack and is now slowly recovering after being treated in an animal hospital.)

Reports claim that killer bees, also known as Africanized bees, were to blame for the attack. But given the buzzing insects' terrifying nickname, how remarkable is it that Fischer survived an attack by a huge swarm?

Related: Do bees really die if they sting you? 

Killer bees were first bred by a Brazilian scientist attempting to combine the vast honey yields of European honey bees with the adaptation to warmer climates of African honey bees, according to London's Natural History Museum. The hybrid bees migrated North from Brazil, through South and Central America to the U.S. Over the years, their aggressive behavior and high tendency to swarm and sting in a group has earned them notoriety and the nickname "killer bees." Contrary to popular belief, though, killer bees' venom is no more potent than that of the European honey bee.

In some cases, a single bee sting is enough to kill someone. In 2009, Ray Shaw, former Dow Jones president, died after being stung by a single bee in his garage. (It's unclear what species the bee was.)

However, individual bee stings, even from killer bees, rarely cause death. Each year, roughly 3% of people who are bitten by insects experience anaphylaxis — a severe, potentially life-threatening reaction. Anaphylaxis can occur in people who know that they are allergic to bee stings, as well as those who don't. According to a 2019 report by the Centers for Disease Control and Prevention (CDC), between 2000 and 2017, there was an average of 62 deaths annually from hornet, wasp and bee stings in the U.S. According to a recent YouGov poll, about 75% of Americans have been stung by a bee. Deaths from bee stings, therefore, are rare.

A recent publication in the journal Clinical Case Reports estimates that 50 to 500 bee stings at one time are enough to kill an adult man. The U.S. Department of Agriculture (USDA), however, estimates the fatal number to be higher, at about 1,100 for an adult and 500 for a child, based on the understanding that the average person can withstand 10 stings per pound (0.45 kilogram) of body weight. Fischer's reported 250 stings, therefore, were likely below the lethal threshold.

Fischer is not the first person to have endured such an ordeal and lived to tell the tale. In 2014, a municipal worker in Texas was stung by an estimated 1,000 killer bees and survived. Also that year, a 71-year-old woman was attacked by a swarm of 80,000 killer bees and lived after also sustaining an estimated 1,000 stings. And in 2015, an Arizona man survived 500 to 1,000 stings following an onslaught of tens of thousands of bees. 

Some, however, have not survived similar attacks: A 23-year-old hiker in 2016 died following 1,000 stings, and a man in Arizona in 2021 died from hundreds of stings.

It is unclear why hundreds of stings are fatal to some people but not to others, although several factors play a role in how a person responds to being stung. 

For people with bee sting allergies, their immune system response to stings can be severe and systemic — affecting the entire body, which can lead to anaphylaxis and death. Studies have shown that body weight, immune status of the victim and age can influence the severity of a person's response to a bee sting. People with bee sting allergies over age 25 are more likely to go into anaphylactic shock following a sting, in part because the allergic reaction to bee venom can grow cumulatively worse the more someone's been stung in their lifetime, according to Boston Children's Hospital.

Common nonallergic reactions to bee stings include painful swelling or redness in the affected area, while allergic reactions can include hives, nausea, light-headedness, stomach cramps, vomiting, diarrhea, low blood pressure and swelling in areas other than the sting site, according to the USDA. The main signs of the severe allergic reaction anaphylaxis are hives with difficulties in breathing and swallowing, according to Seattle Children's Hospital, which advises calling 911 if these symptoms occur.

Colds and other respiratory illnesses are never fun. After the sneezing, sniffles and runny nose fade, one symptom often remains: coughing. But why do coughs sometimes take forever to go away? 

The main reason coughs are long-lasting is due to lingering inflammation, said Dr. Albert Rizzo, chief medical officer at the American Lung Association. This inflammation can have several sources, making it difficult to treat. 

These sources can include viral and bacterial infections that cause airway and nasal inflammation. This inflammation irritates the mucous membranes in the airway and nose and produces mucus — the phlegm and snot associated with colds. Nasal inflammation leads to postnasal drip, which is mucus that drips down the throat from the nose and is a common cause of coughing, according to the National Institutes of Health. 

When particles enter the airway through the nose or mouth they can trigger nerve receptors in the lungs to tell the brain, "That's not what we want down here," Rizzo said. Pressure then builds up in the diaphragm, and air is forcefully expelled, taking dust, food and mucus out with it. 

In addition to nasal inflammation, coughs linger after colds because airway inflammation may take a few weeks to subside, and this time could be extended if someone has had previous lung infections or is a smoker, Rizzo said. 

Related: Should you exercise if you're sick? 

When someone is sick, special immune cells called macrophages and neutrophils help fight infections in the airway. These cells are also inflammatory. Sometimes after a cold ends, these cells remain in the airway and keep it inflamed, which is why coughing can continue after infection, said Dr. Amy Dickey, a pulmonary and clinical care doctor at Massachusetts General Hospital (MGH) and an instructor of medicine at MGH and Harvard Medical School. 

In the meantime, delicate airway tissues can be extra sensitive to particles that enter through the nose or mouth. That’s because there's a complex system of nerves and muscles in the airway, throat and brain that control coughing. "Like if you [use a] reflex hammer on your knee, your leg kicks out. There can be similar types of reflexes in the airway," said Dickey. In other words, viruses and mucus are the reflex hammer and coughing is the kicking leg. Once inflammation goes down, this reflex becomes less sensitive and a cough should disappear.

For coughs that last three to four weeks after sickness there are a few home remedies and behaviors that can help shorten a cough's stay (or at least relieve symptoms). 

If postnasal drip accompanies a cough, nasal saline or nasal steroids can help reduce the inflammation contributing to the drip, Dickey said. These are often available over the counter. Throat lozenges can also help calm the larynx and suppress coughs, she added.

According to a 2021 study published in the International Journal of Cardiopulmonary Medicine and Rehabilitation, research shows that honey and saline can help relieve coughing. However, more studies are needed to confirm the efficacy and safety of natural products.  

While coughing can be nagging, it's crucial to remember that coughing serves an immune function. If irritants and mucus stay in the airways, they can damage the delicate airway tissues or the lungs, or even obstruct breathing. Dickey recommends exercising to stimulate deep breathing to loosen mucus, or taking expectorants that thin mucus and make it easier to cough up. This can help remove those inflammatory irritants.

While it's good to be considerate of other people, said Dickey, sometimes it’s important to let coughs out.   

While a lingering cough is most commonly caused by irritation from inflammation, people should see a doctor if a cough lasts more than three to four weeks and is accompanied by other symptoms like fever, shortness of breath or green and yellow mucus.

If a cough continues on its own for more than eight weeks, a doctor may want to do a chest X-ray or measure lung function to check for COPD, lung cancer, emphysema or other serious diseases, Rizzo said.

Allergies are the sixth leading cause of chronic illness in the United States, according to The American College of Allergy, Asthma & Immunology (ACAAI). 

Some of the 50 million Americans who experience this condition each year will be affected by common seasonal allergies. In fact, approximately 8% of U.S. adults have allergic rhinitis, a condition often called hay fever. Hay fever tends to flare up in spring, summer and early fall. 

Seasonal allergies occur when the immune system mistakes a harmless environmental substance as a dangerous pathogen. In response, the body releases compounds such as histamines, leukotrienes and prostaglandins, which cause common hay fever symptoms, such as sneezing, coughing, runny nose, watery eyes, congestion and fatigue. 

But what substances are most often to blame for hay fever? Here, we discuss the five most common triggers for seasonal allergies in the U.S.  

Related: 7 strategies for outdoor lovers with seasonal allergies

1. Weed pollen

Pollen is a fine powdery substance produced by plants when they reproduce. The male reproductive parts of plants — including the stamens of flowers and the male cones of conifers — release these microscopic grains into the environment. Pollen is transported by the wind, insects or other animals to the female ovule. When airborne pollen gets trapped in the nasal passages of people who are allergic to it, it can cause inflammation and irritation to the nose and eyes, according to Yale Medicine.

Weed pollen is the primary culprit for late-summer and early-fall allergies. According to the Asthma and Allergy Foundation of America (AAFA), common weeds that cause allergic symptoms include burning bush, cocklebur, lamb's quarters, mugwort, pigweed, Russian thistle, sagebrush and tumbleweed. However, top on the list of offenders is ragweed (Ambrosia artemisiifolia). 

Ragweed pollen allergy is a leading cause of seasonal allergic rhinitis in the U.S., according to the Allergy & Asthma Network (AAN). Ragweed plants are found in virtually every region of the United States, but they are particularly abundant in the East and Midwest. These plants pollinate from early August to November, with peak activity in mid-September and October. One ragweed plant can produce up to 1 billion pollen grains that can travel hundreds of miles. In addition to typical hay fever symptoms, ragweed can cause a blistering rash or trigger an asthma flare-up.

2. Grass pollen

Grass pollen, like weed pollen, is lightweight and travels easily through the air. For the northern United States, the grass pollen allergy season lasts primarily from April to June. In the South, some grasses may cause year-round allergies, according to the AAN.

There are hundreds of types of grasses, but only a few cause allergy symptoms. If you are allergic to one type of grass, it does not necessarily mean you will be allergic to others. 

Common grasses that can trigger hay fever in the northern U.S. include Timothy (Phleum pratense), Kentucky blue (Poa pratensis), rye (Lolium perenne) and fescue (Festuca arundinacea). Common grasses that trigger hay fever in the South include bahia (Paspalum notatum), Bermuda (Cynodon dactylon), centipede (Eremochloa ophiuroides), Johnson (Sorghum halepense), St. Augustine (Stenotaphrum secundatum) and multiple Zoysia species, AAN said. 

3. Tree pollen

Tree pollen is the first pollen to appear each year in the United States. In some Southern states, trees can produce pollen as early as January, whereas pollen production usually begins in April in the North, according to the AAFA. Many trees produce pollen through May, which overlaps with the grass pollen season. 

According to the AAN, common tree pollen allergens include oak, maple, birch, cedar, juniper, mountain cedar (Juniperus ashei) and Eucalyptus. Mountain cedar often causes allergies in December in Texas, Oklahoma and other Southern states. The phenomenon is nicknamed "Southwest cedar fever" or "Texas cedar fever." Mountain cedar is known to release so much pollen that it looks like smoke in the air.  

4. Mold and fungus spores

Mold is a type of fungus that reproduces by sending tiny spores into the air. Mold thrives in warm, dark and moist environments. Mold can be found indoors year-round. However, allergy symptoms from fungus spores are most common from July to early fall, according to the AAFA. 

Many types of mold grow on rotting logs and fallen leaves, in compost piles, and on grasses and grains. Mold does not die in cold temperatures. Instead, it becomes inactive during the winter and resurfaces in the spring. Indoors, fungi tend to grow in damp areas, like bathrooms, kitchens and basements. Common types of mold that cause allergy symptoms include Alternaria, Aspergillus, Cladosporium, Penicillium and mildew. Food fungi, like mushrooms or foods containing yeast, do not typically cause allergy symptoms in the nose, eyes and lungs. Reactions to food fungi are often caused by the food's direct effect on blood vessels, the AAFA said. 

5. Dust mites

Dust mites are small eight-legged creatures that belong to the Arachnida class, the same broad taxonomic group as spiders, chiggers and ticks. Hundreds can live in a single gram of dust. They tend to hide in carpets, upholstered furniture, bedding, clothes, soft toys and pet fur. Dust mites live well and multiply easily in temperatures of 68 to 77 degrees Fahrenheit (20 to 25 degrees Celsius). They also like humidity levels of 70% to 80%. 

Dust mite allergies often act up during the colder months of the year, when people spend more time indoors at around the mites' preferred temperature range, according to the AAFA.

Dust mites feed mainly on the tiny flakes of human skin that people shed each day. An average adult may shed up to 0.05 ounce (1.5 grams) of skin per day, which is enough to feed 1 million of these creatures. Both the body parts and the waste products of dust mites can cause allergy symptoms, such as mild difficulty breathing, chest tightness and eczema flare-ups, the AAFA said.  

The first step in addressing a dust mite allergy is to manage the environment, such as wiping surfaces and using zippered, allergen-resistant encasements for pillows, mattresses, and box springs, according to Harvard Health. Over-the-counter allergy medications, such as steroid nasal sprays and antihistamines, can also be helpful. The newest treatment option for dust mite allergy involves sublingual immunotherapy (SLIT), a type of oral medication.

The best air purifiers for allergies can bring relief to your symptoms if you suffer from adverse reactions to airborne pollutants, such as mold spores, pet dander or dust. With hay fever season in full swing, spring is a particularly good time to invest in one of these clever appliances. But which appliance should you choose? Not every best air purifier can trap tiny airborne allergens.

To combat hay fever or pet allergies, your air purifier should be equipped with a High Efficiency Particulate Absorbing (HEPA) filter. "These filters can remove up to 99.97% of small airborne particles, including dust, pollen, and mold spores," Dr. John McKeon, the CEO of Allergy Standards and a principal at the Indoor Air Innovation & Research Institute, told Live Science. Unsure what to look for? Scroll down to our Air purifiers for allergies FAQs and How to choose sections for more buying advice.

Below you can find our hand-picked selection of air purifiers that we think do the best job shielding you from airborne allergens. Our expert reviewers tested each appliance in this guide for at least two weeks and put them through a series of performance tests using an industry-grade Perfect Prime air particle monitor. You can read more about our testing protocol in the How we test section.

Best air purifiers for allergies we recommend in 2026: Rigorously tried and tested

The best air purifier for allergies, overall

The Levoit 600S is our top choice for an air purifier that effectively captures allergens in your home, and with good reason. Not only did it perform well in all of our tests during our full Levoit Core 600S review, but it is also easy to use and packed with handy smart features.

Thanks to its True HEPA H13 and advanced activated carbon filters, this air purifier aced our tests under a number of conditions, removing as much as 99.9% of particles smaller than 0.3 microns at certain times. It is quiet, too. When we measured its noise levels with a decibel-counting app, we did not note more than 55dB, which is quieter than an average refrigerator.

Not only is the Levoit 600S a powerful air purifier, but it also gains points for its discreet design — the toned-up colors and traditional rectangular shape make it easily blend with most home decors. However, some people may find it too bland.

We found that setting up the air purifier is easy thanks to the intuitive controls, and there is plenty of information accessible on the app connected to your purifier, which gives you statistics on historical and current air quality within your home, which we thought was a great feature.

On the other hand, the Levoit 600S is quite a bulky machine, so it may not be suitable for tight spaces. It is also relatively expensive so might not be ideal if you are on a budget — but that said, it's still more affordable than some of the Dyson and RabbitAir models, for example.

• Read our full Levoit Core 600S review

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The best budget air purifier for allergies

If you are on a budget and need an air purifier to tackle your allergy symptoms, then the GermGuardian AC4825E will be an inexpensive purchase that can go a long way to help you breathe more easily. Put simply, it is a whole package for less than $100, making it the cheapest option in this guide.

Complete with a HEPA filter and a charcoal filter to filter odors, this appliance can make your living space a nicer place to be. It is also ultra-quiet, meaning it can work away in the background without distracting you from whatever you are doing. The GermGuardian AC4825E also features a UV-C sanitizer to help remove harmful germs (and that is something we do not see often in affordable air purifiers).

As you might expect with a smaller unit, the coverage of this air purifier is not quite as extensive as bulkier models. It would be suitable for single rooms, rather than expansive spaces, and stands at just 22 inches tall, meaning it will not be too disruptive to your room’s decor, although it is not quite sleek enough to blend in.

There are some other handy features too, including a light to indicate a filter change is due and three speeds including an ultra-quiet sleep mode so that you can keep your machine running into the night.

Most importantly, we were satisfied by its ability to remove harmful particles in our match and incense tests during our full GermGuardian AC4825E review. When put on the highest setting for 15 minutes, it trapped 41% of 0.3 micron particles in the ambient air, 63% after releasing match smoke, and 75% after the insenses were burned. For this price point, it does a good job.

If you want a no-frills, but a very effective air purifier, we would recommend the GermGuardian. However, if you want something more stylish and powerful, you may need to spend more on models like Molekule Air Pro.

Looking for something more pet-friendly? Scroll down to read about the Oneisall Pet Air Purifier.

• Read our full GermGuardian AC4825E review

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Best looking air purifier for allergies

If you are looking for a powerful air purifier with a truly unique design, and you need it to cover larger rooms in your home, then the RabbitAir A3 is the ideal choice for you.

This thoughtfully designed air purifier comes in over 10 colorful designs, and it features a neat mood light that can be automatically switched off at night. More importantly, it boasts excellent air-cleaning performance. Certified Asthma & Allergy Friendly by the Asthma and Allergy Foundation of America, the RabbitAir A3 will easily get rid of pollen, pet dander and many other airborne allergens. And because it is Energy Star Certified, it will not put a strain on your energy bill while doing so.

During our RabbitAir A3 air purifier review, we were thoroughly impressed at its functionality. It is relatively large, but light and compact, and it does not make much noise even when kicked into high gear (maximum 43 dB in our tests). Unlike many other air purifiers on the market, the RabbitAir A3 can also be mounted on the wall, making it a great option for households with pets or small children. We also liked its user-friendly display, and that it was easily controlled via a handy app.

Moreover, the RabbitAir A3 features a whopping five filters, one of which can be customized to suit your specific needs. For example, you can choose a Germ Defense filter to trap harmful microbes, or opt for a Pet Allergy filter to clear your air of pet dander.

There are, however, several downsides to the RabbitAir A3. This air purifier is relatively expensive, and its filter replacements come at a steep price tag. It is also tricky to move around, as it does not feature any handles or ridges.

• Read our full RabbitAir A3 air purifier review

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Best tower fan for allergies

As with any Dyson product, a sleek and well-engineered design was to be expected of the Dyson Purifier Cool PC1 — we think it is one of the most stylish air purifiers on the market. This appliance definitely does not disappoint on those grounds, and has a practical edge too, doubling as a cooling fan, giving you more bang for your buck. True, it is not particularly affordable (it costs around $449, and since it was released relatively recently, it is rarely on sale), but it is still much cheaper than many other Dyson air purifiers. For example, the Dyson Purifier Hot+Cool Formaldehyde costs almost twice as much.

This sleek air purifier performed exceptionally well in our full Dyson Purifier Cool PC1 (TP11) review, with our tests concluding that it often captured more than 90% of monitored particles when used at its highest setting for at least 30 minutes. It picks up microscopic particles smaller than 2.5 microns, meaning it is capable of reducing dust, pollen and other airborne allergens.

In addition, the Dyson Purifier Cool PC1 does a great job as a bedroom fan with its quiet airflow and stylish design. At the lowest fan speed, it is no louder than whispers or leaves rustling in a gentle breeze (25 dB). This also means that this fan-air purifier is less noisy than some of the older Dyson models we have tested (the Dyson TP07, for example, can be as loud as a dishwasher).

If you want your home to be a relief from allergy symptoms, then another neat trick with the Dyson Purifier Cool PC1 is that you can set your machine to start working remotely, all from the comfort of your machine’s app. Smart features on this appliance are top-class. We were particularly impressed by its robust air quality monitoring — an important feature for anyone struggling with asthma and allergy symptoms.

Though this air purifier might not be within everyone’s price range, it has a lot to deliver, and an eye-catching design to sweeten the deal.

• Read our full Dyson Purifier Cool PC1 (TP11) review

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Best air purifier for germs

Large spaces require powerful air purifiers, especially if allergies are your primary concern. The BlueAir Classic Pro CP7i fits the bill — it is best suited for rooms measuring 609 square feet, but it can cover up to a whopping 2,800 square feet, and it boasts one of the highest CADR ratings of all the appliances mentioned in this guide. On the flip side, it is also one of the most expensive. This air purifier costs nearly $700, and its filter replacements will set you back by around $100 at a time. That said, we still stand by our choice. The BlueAir Classic Pro CP7i may not have the awe-inspiring looks of the Rabbit Air A3 or the mind-boggling functionality of the SwitchBot Air Purifier Table, but you would be hard-pressed to find a better unit for large spaces. Here's why.

First and foremost, it is the only air purifier on the market with High-Intensity Narrow Spectrum (HINS) lighting. This technology, often used in healthcare settings like clinics and surgery wards, has been shown to safely and effectively remove viruses, bacteria and other common pathogens. Every 10 minutes, the BlueAir Classic Pro CP7i turns on the HINS lightning to reduce the germs captured on the air filters, thus removing them from circulation.

Speaking of air filters, this air purifier features a pre-filter, a HEPA filter and an activated carbon filter — and it shows. During our full BlueAir Classic Pro CP7i review, we were thoroughly impressed by its ability to remove unpleasant smells and various airborne particulates. This air purifier delivered particularly good results in our smoke tests, sucking up to 99.99% of particles after 30 minutes of running on Auto mode. The cherry on top? It was exceptionally quiet doing so.

Lastly, the BlueAir Classic Pro CP7i boasts several independent certifications, including Asthma & Allergy Friendly, Energy Star and CARB. This air purifier delivers on its claims and has the receipts to prove it.

• Read our full Blueair Classic Pro CP7i review

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Best air purifier for large spaces

The Blueair Blue Signature is our favorite pick for large bedrooms and living spaces, and by a long mile. This air purifier won us over with its exceptionally stylish design, whisper-quiet fans and powerful air-cleaning performance. We also liked how functional it was — the Blue Signature comes with an impressive set of smart features and doubles as a table for books, remote controls and other small trinkets. Not to mention, it is Energy Star certified and highly customizable. We gave it a near-perfect 4.5-star rating in our Blueair Blue Signature review, and if not for its high price (the basic version of this air purifier costs $449.99) and relatively fragile build, we would have given it a full five stars.

The Blueair Blue Signature not only does a good job of trapping airborne allergens, but it also excels at removing bad smells. That is because it is equipped with a patent-pending OdorFence technology — unlike other models mentioned in this guide, it does not trap odor molecules in a carbon filter, but it actively breaks them down using enzymes. According to Blueair, this innovative method is 10 times more effective against lingering smells than carbon filtration alone. While this may sound like a bold claim, this air purifier did make a considerable difference to the air freshness in our home, effectively tackling smoke, cooking smells and cleaning chemicals.

That said, the Blueair Blue Signature may not be the best option for households with cats and/or small children. The fabric pre-filters are easy to damage, plus they have to be regularly washed and changed, and the largely plastic tabletop surface is prone to scratches. If you need something more durable, we would recommend the Levoit Core 600S instead.

• Read our full Blueair Blue Signature air purifier review

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Best air purifier for monitoring air quality

The Molekule Air Pro provides some of the most comprehensive air quality readings we have seen in a commercial air purifier. Unlike most appliances on the market, it tells you exactly how much particulate matter is lingering in the air at any given time, breaking it down into 1-micron, 2.5-micron, and 10-micron particles, volatile organic compounds (VOCs), carbon dioxide and relative humidity. All of the data collected by the Molekule Air Pro can then be viewed in the Molekule app, so you can have a detailed overview of air pollution changes over time. If you like your numbers or are concerned about a specific type of airborne allergens, this air purifier will thoroughly impress you.

It is not just the air quality readings that make the Molekule Air Pro stand out among its competitors. This air purifier is one of the handful of models cleared by the FDA as a Class II medical device under the 510(k) program. That is because it is equipped with a patented pollutant-destroying PECO technology that can turn pollen, dust mites and other organic airborne allergens into water vapor and harmless gases — and it showed in our tests.

During our Molekule Air Pro review, we were impressed by its powerful air-cleaning performance. This appliance did a particularly good job at removing smoke, trapping 99.6% of particles measuring 0.3 microns and 99.9% of 2.5-micron particles after just 15 minutes on Auto mode. The Molekule Air Pro delivered even better results when we repeated this test at its highest fan setting. The problem is, this air purifier was relatively loud when put through its paces, reaching up to a whopping 66dB — as loud as a regular conversation. It can, however, be put in a Quiet Mode.

High cost is another downside. Priced at roughly $1000, the Molekule Air Pro is one of the most expensive models in this guide, and its filter replacements are pricey, too. If you want to monitor air quality at a smaller cost, consider the Levoit Core 600S-P instead.

• Read our full Molekule Air Pro review

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Best air purifier with humidifier

When it comes to air purifiers, Turonic may be a new kid on the block — but do not let that put you off. The Turonic PH950 2-in-1 model may be a strong contender for the title of best mid-range air purifier.

Weighing in at almost 24 lbs, it is definitely not the lightest piece of equipment on the market. It is also bigger and wider than most competitors, so you may need to sacrifice some floor space. But taking into account what the Turonic PH950 can offer, this is not necessarily a deal breaker.

Indeed, the Turonic PH950 is a powerful 2-in-1 machine combining an air purifier and a humidifier. This complex piece of equipment is equipped with an ionizer, UV-C technology and several different filters designed to neutralize up to 99.98% of unwanted particles as small as 0.1 microns. It also comes with 10 different operating modes, a handy remote control, a designated app, a timer, PM2.5 laser air quality sensor, and a child lock — all for approximately $400 per unit. It may sound like a hefty price tag, but we found the Turonic PH950’s performance to be superb in our tests. And since this piece of equipment is highly energy efficient, it will not rack up your energy bills.

During our Turonic PH950 air purifier review, we found it easy to assemble and use. It is equipped with a stylish circular display and easy-to-understand color-coded indicators. The display is also suitable to use in a bedroom at night, as the icons are bright, but not flashy. More importantly, in most of our tests, it reduced as much as 85% of harmful particles within 30 minutes of being put at the highest fan speed.

The downsides? For a relative beginner, the Turonic PH950 may seem like an overly complicated piece of machinery. Changing a filter in this piece of equipment can also prove quite costly — the price for a single filter pad tends to fall between $45 and $60.

• Read our full Turonic PH950 air purifier review

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Best air purifier for homes with pets

A good air purifier for pet owners should be able to do three things: keep hair at bay, remove pet dander and reduce unpleasant smells. The Levoit Vital 200S not only does all of these things, but it does them well. Plus, it comes with useful smart features.

Putting the Vital 200S through its paces during our Levoit Vital 200s review, we found it impressive and efficient at removing particles measuring as small as 0.3 microns. Pet dander, mold, dust and smoke were absorbed while chemicals and odors from everyday household cleaning and cooking were neutralized by the three-stage filtration system. This includes a washable pre-filter, an H13 True HEPA filter and a high-efficiency activated carbon filter.

The Levoit Vital 200S offers four fan speeds, three separate modes including pet, auto and sleep mode, and a connected app that allows you to control your air purifier remotely, wherever you are. It also works with Google Assistant and Alexa voice control devices.

The Vesync app is easy to use and allows users to track their real-time air quality data and historical data, revealing peaks in poor air quality over the day and taking the guesswork out of what is causing bad air quality in your home.

While the boxy design may not be suited to users who want a sleek and stylish air purifier, or those with small rooms, the no-frills aesthetic makes the Levoit Vital 200S a good choice for most users. However, it is not the most affordable option in this guide. If you are a pet owner on a tight budget, consider the GermGuardian AC4825E instead. Or, if you have a curious cat, consider the SwitchBot Air Purifier Table — it is similarly priced, but your furry friend will love it.

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Best air purifier for cat owners

Cats are marvellous creatures: beautiful, intelligent and full of personality. Also, exceptionally curious. No household appliance is safe from their paws — and that includes air purifiers. If you are worried that the aforementioned Levoit Vital 200S may spell disaster for your furry friend, consider the SwitchBot Air Purifier Table instead. With its bite-resistant cord, paw-proof grilles and waterproof tabletop, this quirky appliance was designed with pet owners in mind. Not to mention, it can serve as a convenient vantage point and napping station for your cat.

Indeed, the SwitchBot Air Purifier Table is more of a multi-purpose appliance than a typical air purifier. Unlike the vast majority of air-cleaning appliances on the market, it features a wireless phone charging station, an essential oil diffuser and a skilfully designed ambient light. Its features are nothing short of impressive.

During our full SwitchBot Air Purifier Table review, we were also impressed with its exceptional portability. It weighs only 10.68 lbs (4.85 kg) and is easy to grab hold of. We also liked how quiet it was. When we measured its noise levels with a Sound Meter decibel counting app, we recorded just 21 dB at the lowest fan speed. That is equivalent to leaves rustling in the wind or a quiet whisper. It is a great choice for bedrooms and studies.

However, the SwitchBot Air Purifier Table is not without its flaws. For example, it is not powerful enough to suit large spaces and its air-cleaning performance differs depending on the mode used. Moreover, it is relatively expensive. That said, we still think this unique air purifier is well worth the investment.

• Read our full SwitchBot Air Purifier Table review

Second-best

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Best air purifier for commercial spaces

The AirDoctor AD3500 is our top pick for extra-large rooms and commercial premises. This humble-looking air purifier delivers an immensely powerful air-cleaning performance, covering up to an impressive 1,260 square feet (117 square meters). At the same time, it is exceptionally portable and easy on the energy bill. Interestingly, this air purifier comes in two options — with or without smart features — giving you a choice as to whether you want all the high-tech frills or not.

More importantly, the AirDoctor AD3500 has everything you may need to combat airborne allergens: a pre-filter that traps large particles like dust and hair, a dual-action carbon/VOC filter that absorbs odors and harmful gaseous compounds, and an UltraHEPA filter capable of trapping 99.99% of particles as small as 0.003 microns. For comparison, most air purifiers feature just a standard HEPA filter that can "only" remove particles with a size of 0.3 microns. This appliance is a powerhouse — and it shows.

During our AirDoctor AD3500 air purifier review, we were blown away by its air-cleaning capabilities. This air purifier got rid of nearly all airborne particles in our ambient tests. It did an even more impressive job removing heavy smoke pollution. It only took 15 minutes for the AirDoctor AD3500 to hoover up a staggering 98.9% of 0.3-micron particles and 99.95% of particles larger than 2.5 microns. We also liked how quiet it was. When we measured its noise levels with a decibel-counting app, we did not get a reading higher than 57 dB (equivalent to the sound levels generated by a vacuum cleaner).

However, there are a few drawbacks to the AirDoctor AD3500. It is not particularly good-looking (it looks more like a mini-fridge, as our reviewer noted), and it comes with a relatively high price tag. It can also be expensive to maintain. A one-year supply of filter replacements costs $152.99, which is far more than what most other brands charge.

• Read our full AirDoctor AD3500 air purifier review

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Best eco-friendly air purifier

The IQAir Atem Earth is a thing of beauty — unlike other air purifiers, it is made from sustainably sourced beech wood, giving it a funky and stylish design, rather than being your typical white rectangle or circular appliance. Although it weighs 7.8 kg, we found it easy to move around thanks to its large handle and, for eco-conscious individuals who are fatigued by the throw-away culture we live in now, it comes with a 10-year warranty and a 25-year maintenance and repairability guarantee. Not only is it made from sustainably sourced materials, but it is designed to last, meaning less waste in landfill. A win-win for those wanting to help the Earth.

In terms of performance, the IQAir Atem Earth comes with a HyperHEPA filter that can remove 99.5% of particles, measuring as little as 0.003 microns. Not only this, but it also comes with an activated carbon filter that can help reduce unpleasant odors. The only thing with this air purifier is that it’s expensive to buy ($999), and the high-performance filters do mean that you’re paying up to three times as much for replacements.

For an expensive air purifier, the IQAir Atem Earth is lacking in features — there are plenty in terms of performance, but not a mind-blowing amount for the price tag. It has six manually adjusted fan speeds and an auto mode, where the fan adjusts speed based on its real-time air quality monitoring. The auto mode performed well, with the unit kicking in quickly whenever we cooked or used cleaning products. To control the unit, you have the touchscreen buttons on the top of the purifier, or you can adjust settings via the IQAir AirVisual app. But, if you’re looking for an air purifier with lots of smart features, this one won’t suit you. And the same goes if you’re looking for lots of data on air quality — it only measures two metrics: the indoor/outdoor Air Quality Index and PM2.5 (airborne particles that measure 2.5 microns in diameter).

If you’re looking for a quiet, eco-friendly and stylish air purifier, the IQAir Atem Earth is a strong contender.

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Best air purifiers for allergies: Comparison

Our expert consultants

Best air purifiers for allergies: Frequently Asked Questions

Everything you need to know about air purifiers for allergies

Do air purifiers help with allergies?

Do air purifiers help with allergies? In short, yes they can. These appliances can be effective at trapping the small particles that trigger allergies, preventing them from circulating in the air and then being inhaled. However, air purifiers are not a complete solution, and there are several reasons why.

Hay fever can be triggered by a wide range of airborne substances, but it’s predominantly caused by pollen, Dr. Sameer Nakedar, a medical doctor and chief medical officer at Welzo, a personalized healthcare provider based in London, England, told Live Science. ”The most common allergens that cause hay fever include tree, grass and weed pollen. Grass pollen is by far the most common, it affects up to 95% of sufferers,” he said. Mold spores and animal dander can also contribute to hay fever symptoms. “However, these allergens are not specific to hay fever, and they can trigger allergic reactions in some people all year round,” Nakedar said. Pollen, animal dander and other common indoor allergens are relatively large particles. According to the U.S. Environment Protection Agency (EPA), “some controversy exists about whether air cleaners can reduce the allergic reactions” produced by such sizable allergens. They don’t tend to linger in the air, but rather end up settling on surfaces in the home, such as cushions or carpets. Air purifiers may not be able to remove these allergens unless they are “disturbed and re-suspended in the air,” EPA said.

Complicating the situation, two individuals with the same allergy may have vastly different reactions to the same amount of allergens present in the air. Some people may experience mild symptoms, while others may have more severe or persistent issues, Nakedar said. As a result, it is likely that the same air purifier may have a different impact on hay fever symptoms, depending on one’s sensitivity to allergens.

Moreover, air purifiers are not created equal. They come in many shapes and sizes and with many different technological solutions. Therefore, some air purifier models may be better at easing allergic reactions than others. For example, machines equipped with HEPA filters may be more effective at reducing airborne allergens than air purifiers which use different filters. According to the EPA, High Efficiency Particulate Air Filters, commonly known as HEPA, have been shown to reduce at least 99.97% of dust, pollen, mold, and any other airborne allergens with a size of 0.3 microns (µm). At the same time, some HEPA filters are more complex than others, and it is likely that such differences in the design have an impact on their overall effectiveness.

Are air purifiers or humidifiers better for allergies?

Air purifiers vs humidifiers: what is best for airborne allergies? Both appliances can ease some of the symptoms associated with these conditions.

Abbas Kanani, a superintendent pharmacist at Chemist Click, an online pharmacy, told Live Science: “Dry air can exacerbate respiratory conditions and allergy symptoms, as it can irritate the nasal passages and throat,” he said. “Humidifiers work by adding moisture to the air to combat dryness. By increasing humidity levels, they can help alleviate dryness, soothe irritated airways, and provide relief for nasal congestion and dry coughs. A combination of both a humidifier and an air purifier may be beneficial in some cases, particularly during the winter months when indoor air tends to become dry due to heating,” Kanani said.

However, humidifiers may not be suitable for people with dust mites and mold allergies, according to the AAAAI. Mold spores tend to grow rapidly in places with excessive moisture, such as bathrooms, roofs or windows. Dust mites - microscopic, insect-like pests that feed off dead human skin cells - also thrive in humid environments. According to the EPA, humidity levels above 60 percent may vastly increase the number of these allergens in the environment, while levels between 30 and 50 appear to keep dust mites and mold spores at bay. Unfortunately, many humidifiers do not come with humidity meters and extensive moisture control settings, which makes it more difficult to adjust their output.

In addition, humidifiers themselves may add to the mold problem, AAAAI said. If the filters are not cleaned or changed on a regular basis, it can create a perfect environment for mold spores to grow within the unit. This in turn can lead to humidifiers blowing a vapor containing a high number of allergens. To prevent that from happening, the AAAAI recommends using distilled or demineralized water. Minerals found in tap water may increase the growth of pathogens and spores, as well as create white dust that can irritate the sinuses and contribute to allergy symptoms.

How to choose the best air purifier for you

How to choose an air purifier? There is no single answer to this question. That said, certain features may be more important than others if allergies are your main concern.

While all air purifiers are designed to remove harmful particles from the air, not all models can ease your allergy symptoms. Seemingly similar models may use different filters and offer vastly different technological solutions. This can make some air purifiers way more effective at removing specific airborne allergens than others. When choosing a model, look out for certain features. If your aim is to reduce allergens in your home, your best call is to pick an air purifier equipped with a HEPA filter, Nakedar told Live Science.

HEPA filters, short for "High Efficiency Particulate Air [Filter]", are mechanical air filters composed of a mesh of randomly placed fibers. According to the U.S. Environmental Protection Agency (EPA), HEPA filters have been shown to remove at least 99.97% of airborne allergens with a size of 0.3 microns (µm), including pollen and mold spores. It needs to be stressed, however, that most studies into HEPA filters were conducted in highly regulated laboratory conditions, and there are only a handful of studies that investigated the effectiveness of HEPA filters in reducing allergy symptoms in human subjects. Nevertheless, the results are promising. For example, a 2020 clinical trial published in the Yonsei Medical Journal found that patients with dust mite allergy may need fewer allergy medications following six weeks of exposure to air purifiers equipped with HEPA filters.

Moreover, certain air purifier models may actually exacerbate your allergy symptoms, rather than alleviate them, ACAAI said. For example, ionic electrostatic air purifiers work by releasing ions - molecules with an electric charge due to the loss or gain of one or more electrons - which then force harmful airborne particles to stick to walls and other household surfaces. Although this helps to clean the air from allergens, it does not remove them permanently. Moreover, ionic air purifiers are known to produce ozone, a gas molecule composed of three oxygen atoms, ACAAI warned. And according to the American Lung Association (ALA), ozone can irritate the airways and nasal passages, increasing the risk of respiratory problems and potentially aggravating hay fever symptoms. In addition, some ionic air purifiers come with additional UV light, which aims to kill bacteria and other harmful pathogens. However, there is no scientific evidence that this feature can be effective for alleviating allergic reactions, ACAAI said.

If you are unsure whether an air purifier is suitable for people with allergies, check whether it has been independently tested. "For example, CERTIFIED Asthma and Allergy Friendly air cleaners have been tested to show they remove more than 90% of airborne allergens like cat dander and dust mite allergens," McKeon said. "This certification mark also ensures the product meets AAFA’s high standards," Przywara noted.

Another feature to look out for is the Clean Air Delivery Rate, or CADR, according to The American College of Allergy, Asthma & Immunology (ACAAI). The CADR value measures how fast a certain number of airborne particles can be trapped by an air purifier. Even the most technologically advanced air purifier may struggle with removing allergens if it’s not big or powerful enough to cover enough space. When picking your model, make sure its CADR matches the size of the room where you intend to use it, ACAAI recommends.

Lastly, choose an air purifier that comes with affordable replacement filters, Kanani told Live Science. Filters need regular changing to maintain the device's efficiency, which is particularly important during heavy pollen season, he said.

How we tested these air purifiers

How we test the best air purifiers for allergies

Our reviewers. We know a great deal about the best air purifiers for allergies — many of our expert reviewers know firsthand what it is like to struggle with adverse reactions to pollen, pet dander, mold spores and other airborne allergens. We have spent years trying and testing different appliances, in the everlasting pursuit of an air purifier that can truly help us keep our allergies at bay. You can put trust in our verdicts, because we use these appliances ourselves and we can personally vouch for their reliability.

However, we know that our word may not be enough. Not to mention, everyone has their own unique set of allergic triggers — what works wonders for one person may not work for someone else. So to be as objective as possible, we tested each air purifier in this guide to the exact same standards, using the same procedures and review protocols.

Design. When assessing the design of an air purifier for allergies, we take into account multiple different factors. First and foremost, we make sure that the unit is equipped with a HEPA-style filter capable of trapping miniscule airborne pollutants. Once this condition is met, we look into the size, looks and ease of use of the air purifier in question. Then, we check whether it comes with any additional allergy-busting measures, such as pre-filters and pollutant-destroying technologies. We also look into the energy consumption of the unit, the cost of replacement filters and the terms of the warranty.

Features. We take a good look at the features of an air purifier to fully understand what this appliance has to offer. Does it come with an ionizer, UV sanitizer and other potentially helpful add-ons? How many modes and fan speeds does it have? Can it be operated remotely? Does it come with an air quality monitor, and if so, how detailed are the readings? Also, does it have any smart features or connected apps? Then, we give our verdict on the functionality of the air purifier in question.

Performance. This is the most in-depth part of our testing process. We conduct multiple performance tests using an industry-grade Perfect Prime AQ9600 air particle monitor, a device capable of detecting airborne pollutants as small as 0.3 microns — which is the size of many allergens and tobacco smoke particles. We want to know exactly how much of particulate matter the air purifier can remove, and whether there are any circumstances that can impede or speed up the purification process.

We start by running an ambient air quality test. We put the air purifier in an enclosed, medium-sized room in a home, take baseline air quality measurements, and then run it for half an hour on different settings (including an auto mode when applicable). We make note of air quality readings after 15 and 30 minutes, then calculate the percentage of particulate matter removed by the air purifier. We also measure the noise levels generated by the fan, to comment on how noticeable the purifier will be in an average home.

Next, we conduct smoke tests. We burn a bunch of matches and incense sticks to generate heavy pollution, then run the air purifier for half an hour on the highest fan settings (and auto mode, if applicable). We make note of changes to air quality readings after 15 and 30 minutes, then calculate the percentage of particulate matter removed by the machine. Lastly, we repeat the tests in different rooms to fully assess the appliance's capabilities.

What the users say. Finally, we check online user reviews to see what people think about their air purifier, and we test for any persistent problems or defects that we read about.

As per our testing policy, we fully disclose all our findings in our reviews.

Latest updates

February 5, 2026: We added the Oneisall Pet Air Purifier as the second-best budget option.

November 21, 2025: We added the Blueair Blue Signature as the best option for large spaces.

October 2, 2025: We added the Alen BreatheSmart 35i as the second-best option for air quality monitoring.

June 13, 2025: We added the Dyson Purifier Cool PC1 as the best tower fan for allergies.

May 14, 2025: We added the BlueAir Classic Pro CP7i as the best option for large rooms.

April 4, 2025: We added the SwitchBot Air Purifier Table as the best option for cat owners.

Cow’s milk allergy is one of the most common food allergies in infants and adults, but not many people know what causes it or how it shows. Milk allergy is sometimes confused with lactose intolerance, but while these conditions are both triggered by consuming dairy products, they don’t share the same causes or symptoms. They also require different treatments. 

If someone has a milk allergy, their immune system considers certain proteins in cow’s milk as invaders. In order to neutralize this perceived danger, it initiates a potentially life-threatening allergic reaction. Lactose intolerance, on the other hand, is rooted in problems with breaking down and digesting lactose, which is the main sugar found in dairy products. 

As milk allergy tends to manifest in infancy, knowing how to recognize the symptoms early on is important for parents and carers. We’ve created a guide to milk allergy to help you have a better understanding of the causes, symptoms and treatment options for this common condition.

What is a milk allergy?

According to the National Institute for Health and Care Excellence, milk allergy is an immune-mediated allergic response to one or more proteins in cow's milk, such as casein and whey. There are three different types of milk allergy, depending on the underlying immune mechanism and timing of symptoms: (Ig)E-mediated, mixed IgE and non-IgE mediated. 

An immunoglobulin (Ig)E-mediated allergy happens when a person starts producing serum-specific IgE antibodies immediately after being exposed to trigger proteins. This type of milk allergy produces instant and consistently reproducible symptoms. Adverse reactions typically occur up to two hours after eating dairy products, but usually within 20–30 minutes. 

A non-IgE-mediated food allergy does not involve the production of specific antibodies and reactions to this type of milk allergy are typically delayed. They usually manifest between two and 72 hours after the ingestion of cow’s milk. Mixed IgE and non-IgE allergic reactions involve a combination of IgE and non-IgE responses and are usually delayed.

Lactose intolerance happens when your body is unable to properly digest lactose. Lactose cannot be absorbed in the body in its primal form – it needs to be broken down to glucose and galactose first. The digestive enzyme responsible for this is called lactase. One of the main reasons behind lactose intolerance is the inability to produce enough of this compound. As a result, undigested cow’s milk sugar passes to the colon, where it’s taken up by intestinal bacteria. This process increases the amount of fluid and gas in the gastrointestinal system, causing symptoms like diarrhea, flatulence, bloating, stomach cramps and fatigue. 

It’s estimated that between 2% and 3% of children below the age of three are allergic to cow’s milk. According to the National Institute for Health and Care Excellence, risk factors include sex (boys are twice as likely to suffer from milk allergy than girls), atopic conditions (such as asthma and atopic eczema), a family history of food allergy and/or family history of atopy. Some may also cross-react to proteins found in goat, ewe, horse, camel, and buffalo milk.   

• Related: Dairy-free diet

Milk allergy: causes and symptoms

According to the National Institute of Health and Care Excellence, the underlying mechanism behind milk allergy is not known, but it is thought that various genetic and environmental factors may play a part. Immunoglobulin (Ig)E-mediated cow's milk allergy is expressed by the production of specific IgE antibodies in response to cow's milk proteins. These antibodies bind to the surface of cells in the body, causing a release of cell mediators (such as histamine) that directly trigger the onset of the clinical symptoms. Whereas non-IgE-mediated cow's milk allergy is thought to be mediated by malfunctioning T-cells – a type of white blood cells essential to the functioning of a healthy immune system. 

According to The American College of Allergy, Asthma and Immunology, common milk allergy symptoms include hives (an itchy rash), upset stomach, vomiting, bloody stools and in the most severe cases, anaphylaxis. Symptoms of anaphylaxis include swelling of the airways, reduced ability to breathe, and a sudden drop in blood pressure, causing dizziness and fainting. 

How can you treat a milk allergy?

If you suspect that your child may be suffering from a milk allergy, it’s essential to consult a medical professional and obtain a correct diagnosis. Your doctor will ask questions to get a good understanding of your child’s medical history. They may also perform tests that can detect the presence of immunoglobulin E (IgE) antibodies, such as skin-prick or blood tests. 

Your doctor may also ask for your permission to do a test called an oral food challenge. Under stringent medical supervision, your child will be given small amounts of a substance containing milk proteins to see if any reaction develops. Your doctor will be able to confirm the diagnosis based on all of the collected measurements.  

There are no effective pharmaceutical treatments for cow’s milk allergy. The only way to effectively manage this condition is to avoid dairy products and foods containing cow’s milk proteins. 

Under the Food Allergen Labeling and Consumer Protection Act of 2004, food manufacturers in the US are legally required to include the presence of cow’s milk and cow’s milk components on their ingredient labels. 

If your baby is too little to eat solid foods, your doctor or dietician will recommend you the most suitable baby formulas. To prevent anaphylaxis, patients with milk allergy (or their carers) are advised to carry a so-called EpiPen: an auto-injector containing epinephrine (adrenaline). Immediate application of EpiPen is the only treatment that can stop the life-threatening symptoms of anaphylactic shock. 

Another dietary modification that could help some with milk allergy is using baked cow’s milk. Baked milk refers to milk that has been extensively heated to disrupt the structure of the allergen proteins. Results from a 2017 study suggest that the majority of children under the age of two can tolerate baked milk products in their diet. Some studies indicate that drinking baked milk could help them outgrow their milk allergy quicker. But according to a review published in The Clinical and Experimental Allergy journal, there is little evidence to support this claim.

Can you grow out of a milk allergy?

According to a review published in the Nutrients journal, up to 75% of affected children will eventually outgrow a milk allergy by the time they’re five years old. Milk allergy symptoms are most likely to continue in those who have high levels of cow’s milk antibodies in their blood. Your doctor will be able to advise you if and when is the right time to reintroduce dairy products into your child’s diet. 

As children outgrow their milk allergy, they begin to tolerate lightly cooked milk and fermented dairy products. The quantity of cow’s milk that is safe often gradually increases. However, the speed of recovery and the amounts that are tolerated can vary significantly between different individuals. To minimize the chances of adverse reactions, it’s always good practice to reintroduce dairy products following a consultation with a medical professional or dietician. 

This article is for informational purposes only and is not meant to offer medical advice.

If you have an unpleasant reaction every time you eat a certain food, you may wonder whether you have some form of a food sensitivity. But what’s the difference between an allergy vs an intolerance, and how can you identify which one you might be suffering with?

It’s easy to get confused, as these conditions present themselves in similar ways. Food allergies and food intolerances may appear in response to the same dietary triggers, and they both produce similar symptoms, such as stomach cramps, diarrhea and skin rashes. But the underlying mechanisms behind these conditions couldn’t be more different, and getting the right diagnosis is essential if you want to receive the right treatment.

In this article, we’ll answer all of your important questions about food allergies vs intolerances, from causes through to treatments.  

What is a food allergy?

According to the American Academy of Allergy, Asthma and Immunology, a food allergy is a chronic condition involving an abnormal reaction to an ordinarily harmless substance. A typical example would be milk allergy. Your immune system views the allergen as an invader and initiates a chain reaction to ‘neutralize’ it. It prompts white blood cells to produce what are known as IgE antibodies, which attach themselves to cells in our body, causing a release of potent chemicals. One of these chemicals is called histamine. 

When the level of these chemicals starts rising rapidly, we experience a range of unpleasant or even dangerous symptoms. Common signs include itching in the nose, roof of the mouth, throat and eyes, runny nose and tearing eyes. Food allergies may present with vomiting, diarrhea and breathing problems immediately after ingesting a substance too.

In severe cases, a person affected may go into anaphylactic shock. This is a potentially life-threatening condition that can be cured with an immediate shot of a drug called epinephrine.  

According to a review in Clinical Reviews in Allergy & Immunology, there are three types of food allergy: IgE mediated, mixed, and non-IgE mediated. They present different symptoms and require different diagnostic tests. Non-IgE-mediated food allergy includes a wide range of diseases, such as atopic eczema, inflammation of the digestive tract, esophagitis and celiac disease. Symptoms usually start appearing early on, with researchers suggesting that up to 20% of infants may suffer from one of these conditions. The most common food allergies in children include milk, egg, soy, wheat, peanuts, tree nuts, fish, and shellfish. Milk and egg allergies are usually outgrown, but nut allergies tend to persist. 

According to data, at least 26 million US adults have a food allergy. However, they're not spread evenly across the population. Electronic health records suggest that the prevalence of food allergies and intolerances may be almost twice as high in females than males, and that Asian ethnicities seem to be the most affected group.

What is a food intolerance?

According to the American Academy of Allergy, Asthma and Immunology, a food intolerance occurs when a person has difficulty digesting a particular food nor nutrient. A typical example would be lactose intolerance. This can lead to symptoms such as intestinal gas, abdominal pain or diarrhea. Based on the data from multiple studies, food intolerances may affect up to 20% of US adults. 

Scientists point at pharmacological effects of food components, non-celiac gluten sensitivity or enzyme defects as potential causes of this chronic condition. There is also a growing understanding of the role that short-chain fermentable carbohydrates (FODMAPs) may play in triggering symptoms. Food intolerances are commonly linked to irritable bowel syndrome, but as scientists from the Nutrition Journal point out, there’s no conclusive evidence that this is the case. 

The three most common food intolerances are lactose intolerance (a type of sugar found in dairy products), casein intolerance (a type of protein found in dairy products) and gluten intolerance (a type of protein found in grains such as wheat, rye, and barley). 

• Related: What is exercise intolerance?
• Related: Diary-free diet

What is a food sensitivity?

According to Harvard Medical School, food sensitivities encompass unpleasant symptoms that routinely happen after you’ve eaten specific foods, but they’re not related to food intolerances, food allergies or celiac disease. A typical example would be caffeine sensitivity. There is a lot of controversy surrounding these conditions, as not much is known about their origins. It appears that exposure to specific foods may trigger a strong non-allergic immune reaction that in turn generates symptoms such as joint pain, stomach pain, fatigue, rashes, and brain fog. These symptoms are not life-threatening, but they can significantly affect your quality of life.

Food sensitivities are not permanent conditions and they can diminish after some time. It’s been suggested that the reduction or increase in symptoms may be due to changes in the functioning of our immune systems or the composition of our gut bacteria.

Diagnosing an allergy

Diagnosing an allergy, food intolerance or food sensitivity can involve several steps. Your doctor is likely to ask you questions to get a better understanding of your personal and medical history. They may perform a physical exam, and you may be asked to undergo a lung function test to detect how well you exhale air from your lungs. In certain cases, an X-ray of your lungs or sinuses may be needed.

Skin tests

Skin Prick Test (SPT) can be one of the most accurate and least expensive ways to confirm your susceptibility to allergens. A small drop of the possible allergen is placed on a patch of skin that is then lightly pricked or scratched with a needle. If you are sensitive to the allergen, within 15 minutes you will develop symptoms such as redness, swelling and itching. You may also see the affected area raised and inflamed (the so-called ‘wheal’). In general, the larger the wheal, the more likely you are to be allergic to the substance. However, a positive result alone does not indicate a diagnosis. 

Patch tests

Patch tests are used to determine which allergens may be causing contact dermatitis. A small amount of a possible allergen will be placed on your skin and then covered with a bandage. Your doctor will check for any possible skin reactions after 48 to 96 hours.  

Blood tests

 Blood tests tend to be used when you have a skin condition or are taking medicine that interferes with skin testing. Your blood sample will be measured against the amount of antibodies your blood cells produce to neutralize the allergens. This test is called Specific IgE (sIgE) Blood Testing (sometimes referred to as RAST or ImmunoCAP testing). Although it may sound like a reliable and accurate method, blood tests produce a lot of false positive results so can’t be used to diagnose an allergy alone.

Challenge/ Provocation Tests 

Challenge tests are done under close supervision of a qualified medical professional. You inhale or eat a small amount of allergen and a physician monitors your reaction, stepping in if you start going into anaphylactic shock. Since provocation tests carry a large risk to your health, certain conditions have to be met before you’ll be allowed to do them. 

Allergy treatment

The most effective way to avoid the symptoms of food allergies is to remove the allergens from your diet and immediate surroundings. According to The Food Allergy Labeling and Consumer Protection Act of 2004 (FALCPA), food manufacturers based in the United States must clearly state on the packaging whether their product contains any of the eight most common food allergens: milk, egg, wheat, soy, peanut, tree nut, fish and crustacean shellfish. When a food item was made without using these allergens, producers must signal whether there was a chance of cross-contamination during the production process. 

You need to remain vigilant, particularly if you have a severe allergy that increases your risk of going into an anaphylactic shock. Make sure to carefully check food labels, learn what you need to avoid and always ask for a list of potential allergens when dining out. Also, be mindful that you may come into contact with allergens in cosmetics, hair products and other health and beauty aids.

Anaphylaxis

Going into an anaphylactic shock is extremely dangerous and the only effective treatment is an immediate epinephrine (adrenaline) shot. That’s why many food allergy sufferers are prescribed emergency epinephrine auto-injectors, commonly referred to as EpiPens. It’s good practice to always have two doses available to hand, as this severe reaction can recur in about a fifth of affected individuals. 

Adrenaline needs to be injected as soon as you start experiencing symptoms such as trouble breathing, coughing, dizziness, hives, tightness in your throat, rashes, vomiting, diarrhea or abdominal pain. 

Diagnosing and treating food intolerances

Managing food intolerances and sensitivities can be more complicated than food allergies. You may need to spend a lot of time observing your body and experimenting with your diet. One strategy is to remove the foods you believe may be causing adverse reactions for a two to four week period, and then reintroduce them to watch for potential symptoms. 

It’s advised to have a qualified medical professional or nutritionist monitor your progress and guide you on your path to recovery. You may need to stick to a strict diet to make sure your negative symptoms don’t come back. 

There’s also evidence that targeting your gut health could help aid your food intolerances. Maintaining a gut-friendly diet and taking probiotics helps many sufferers keep their conditions at bay. 

According to a review published in the Critical Reviews in Food Science and Nutrition, live bacteria and yeast supplements may ease the symptoms of lactose intolerance. There’s also evidence that regular probiotic consumption can help people with gluten sensitivity, as indicated in the Current Opinion in Clinical Nutrition and Metabolic Care journal.     

This article is for informational purposes only and is not meant to offer medical advice.

Those who suffer with hay fever know that it can make the otherwise enjoyable transition from winter into spring a nightmare. Along with the warmer weather and sunshine can come symptoms such as a runny nose, sneezing and eye irritation.

Trees and grasses release their pollen from April to June, making this the peak time for those with hay fever to experience symptoms. Some trees, such as willow, start releasing pollen as early as February, and some weeds continue well into September. While you may not be sensitive to all types of pollen, on days with a high pollen count (a measure of the average number of pollen grains per cubic meter squared) you may find yourself experiencing unpleasant symptoms. 

Some ways to reduce your hay fever symptoms include antihistamines or steroids, whether in pill, drop or spray form. You can also reduce the amount of pollen in your indoor environments with one of the best air purifiers, which help to trap the pollen before it can irritate your immune system.

What is hay fever?

Max Wiseberg, airborne allergens expert and creator of HayMax, explains that hay fever or seasonal allergic rhinitis is an allergic reaction to pollen. “Most people who suffer from hay fever are allergic to grass pollen and many are allergic to tree pollen,” he says. “Hay fever is a result of our immune system’s overreaction to innocuous antigens such as pollen. These antigens stimulate the bodies’ mast cells, which then break or degranulate, releasing mediators that include histamines. These mediators can cause the unpleasant itching, redness, inflammation and other hay fever symptoms.”

Hay fever symptoms may also include an overall achy feeling, or build-up of pressure in the entire face area. “The sinus area is often the most painful,” says Wiseberg. “Constant nose rubbing and blowing can leave sufferers with skin irritation and sensitivity. All of this can lead to tiredness, fatigue and exhaustion.” 

Hay fever can also cause difficulty getting to sleep and other sleep disturbances. “These symptoms can in turn zap your energy levels, leaving you feeling low and sluggish,” adds Wiseberg. “Chronic hay fever sufferers may experience more severe or prolonged symptoms.”

Need a hand breathing easy during the warmer months? Check out our guide to the best air purifiers for allergies to trap unwanted allergens and pollutants.

• Related: Why don't we breathe equally out of both nostrils?

Hay fever symptoms

Hay fever symptoms are caused by our immune system’s response to the perceived threat of pollen in our system. Although most pollen isn’t harmful to us, our immune systems detect microscopic particles of pollen entering our respiratory system when we breathe and set off immune responses to try and clear it. That’s why your eyes and nose itch and run, and you might sneeze or cough as your body tries to get rid of the pollen. 

Some common symptoms of hay fever are:

• Sore, swollen eyes
• Running or congested nose 
• Sneezing and coughing 
• Itchy nose, mouth, throat, ears and eyes 
• Tiredness and fatigue 
• Sinus pressure  
• Headaches 

If you suffer from asthma, you may find that pollen is a trigger for your asthma symptoms. A study in the Annals of Otology, Rhinology & Laryngology found that hay fever commonly occurs in those with asthma. 

• Related: How can air purifiers help with asthma? 

Hay fever: Tests and diagnosis

If you have one or a combination of the above symptoms at the same time each year, you can be fairly certain you have hay fever. Most treatments are over-the-counter, but it might be worth talking to a professional to ensure you’re choosing the right one for you.

Wiseberg advises. “There are many tests available but the best way to diagnose hay fever is to talk to your doctor or pharmacist, and then to ask them to test,” he says. “If your allergy is bad, you should ask for a referral to an allergy specialist.” 

How can you treat hay fever?

Whilst there is no ‘cure’ for hay fever, there are several options for managing it. You may find some work for you better than others, so it’s all about finding the right treatment for you. #

“Several different groups of medicine have been developed for treating allergies,” says Wiseberg. The common ones are:

• Antihistamine tablets and capsules – these can relieve most hay fever symptoms, including sneezing, itchy, runny eyes, skin irritation, itchy nose and throat, but are less effective for nasal congestion. 
• Antihistamine nasal sprays – these can quickly ease itching, sneezing and watering but generally only provide proof against mild symptoms. 
• Steroid nasal sprays and drops – these reduce inflammation in the nose; they work best for clearing nasal symptoms such as itching, sneezing, watering and congestion. Sprays sometimes clear eye symptoms too. 
• Eye drops – may reduce itchy, watering, swollen eyes. 
• Other, slightly less common forms of conventional medicine for hay fever include nasal washes. 

Most tablets, sprays and drops can be taken individually or in combination to help combat the symptoms of hay fever. 

“And, just as with other drugs, there are many different brands of each type of hay fever medicine, so don’t give up if the first one you try doesn’t work for you; you may well find another version that works better,” adds Wiseberg.

Can you grow out of hay fever?

Hay fever is unusual in that sometimes symptoms can improve with age. This may be due to low level exposure to allergens over time developing tolerance in our immune systems, so those who have hay fever as children may not suffer – or suffer as much – as adults. A study in Allergy and Asthma proceedings found that when checking in with participants twenty three years after the original study, the majority (84.8%) reported improvements in their hay fever symptoms.

References

Additional disease burden from hay fever and sinusitis accompanying asthma, Annals of Otology, Rhinology & Laryngology, 2009

Natural history of hay fever: a 23-year follow-up of college students, Allergy and Asthma proceedings, 1998 

Many people decide to invest in air purifiers to help ward off seasonal allergies, like the hay fever that flares up in spring, summer and early fall. These appliances are capable of removing the pollen particles behind seasonal allergies from the air.

But do air purifiers help with dust? And more specifically, can they reduce the symptoms of dust mite allergies?

In short: yes, but only slightly.

Dust mites are microscopic arachnids that commonly live in household dust, feeding on flecks of skin shed by humans and their pets. The tiny pests lurk in soft surfaces, such as bedding, carpets and curtains, and they can aggravate people's allergies.

That's because, although people often assume dust itself sets off their allergies, it's particles left behind by dust mites that are usually to blame. It is typically proteins in the dust mites' droppings, rather than the mites themselves, that cause allergy symptoms.

Once the dust mites have had a good gnash of your dead skin cells, the enzymes they use to break down the food come out the other end in small fecal pellets, which are incredibly potent allergens, Dr. Jay Portnoy, head of allergy, asthma and immunology at Children's Mercy Hospitals and Clinics in Kansas City, Missouri, told Live Science. These droppings get caught up in so-called dust traps, such as carpets, rugs, blankets and curtains.

Dust mites do not tend to float in the air like fine dust particles, although the allergens they leave behind in dust can get stirred up when people vacuum or sweep.

While air purifiers are effective at removing the majority of the offending allergens from a single room, they do not take away all the airborne particles, Dr. Alana Biggers-Walker, associate professor of medicine at the University of Illinois Chicago, told Live Science. And they don't get at the root of the problem: the dust mites and the dusty furnishings they live in.

Nonetheless, according to a meta-analysis published June 2024 in the World Allergy Organization Journal, air purifiers may significantly reduce some of the symptoms of dust mite allergies, including sneezing and runny nose. But these benefits are only seen when the filters are used overnight and in the "breathing zone," meaning in very close proximity (within a 30 centimeters or 10 inches radius) to a person's nose and mouth.

Ultimately, though, the review suggests that this nighttime air purification may still be less effective than taking extensive control measures over your bedroom's cleanliness — by using mite-resistant bedding covers, cleaning soft furnishings frequently and vacuuming carpets thoroughly.

• Related: How to get rid of dust mites?

The takeaway? While there is some evidence that air purifiers can help reduce the symptoms of dust-mite allergies, they should not be considered as a main line of defense against this common household pest, scientists have concluded. Live Science has reviewed the best air purifiers and recommends models with HEPA filters as they tend to be the most effective at removing tiny dust mite allergens from the air.

This article is for informational purposes only and is not meant to offer medical advice.

Related stories:

— Do air purifiers help with allergies?

— How can air purifiers help with asthma?

— Do air purifiers help with mold?

Dehumidifiers can help improve air quality at home, but do dehumidifiers help with allergies? We do know that reducing humidity in our homes can significantly protect our health, including reducing asthma symptoms and irritation. It's also been observed that dehumidifiers help with snoring.

Dehumidifiers achieve this by ensuring humidity levels remain healthy, stopping the spread of dust mites, mold, and more. In this article, we explore whether dehumidifiers help with allergies, and if they help to make a home happier and healthier for sufferers.

You'll also find plenty of other helpful articles on dehumidifiers here at Live Science, including Do basements need a dehumidifier? and how to clean a dehumidifier. You can also check out some of our top rated models in our guide to the best dehumidifiers. 

Do dehumidifiers help with allergies?

The quality of the air we’re breathing is getting worse, scientists have warned. "The rate at which indoor air is exchanged for fresh air is now 10 times lower than it was 30 years ago," warned scientists in the BMJ in 1998. This leads to increases in humidity that are harmful to our health, particularly for those with allergies and chronic conditions such as asthma.

So do dehumidifiers help with allergies? Yes, and here’s how.

Dehumidifiers work by removing excessive moisture from the air and ensuring relative humidity remains at a stable level. The EPA advises that an optimum level for relative humidity is between 35-50%. At this point, they inhibit the growth of dust mites, a microscopic organism responsible for the majority of allergic reactions.

Dehumidifiers fitted with a high-quality HEPA filter or a filter with an anti-bacterial coating can impact seasonal allergies­­ (Urologic Nursing) caused by exposure to irritants, such as grasses and especially pollen in the air. As the air is drawn through the dehumidifier, particles are captured in the filter, purifying the air. As well as pollen, some dehumidifiers are also fitted with pet hair filters that can reduce – but not remove – the presence of pet hair in the environment, reducing allergies and irritation.

Do dehumidifiers help with dust mites?

Dust mites are the biggest cause of indoor allergies, scientists have found (the BMJ). Dogs and cats fill out the top three places. Populations of microscopic dust mites proliferate in humid environments and can lead to the tell-tale signs of an allergic reaction to dust mites, according to the Asthma and Allergy Foundation of America (AAFA), including a stuffy nose, itchy eyes or skin, or wheezing and coughing.

Dust mites grow best at high humidity levels, says the AAFA. So think your cooler home is safe? Think again. A 2003 PubMed survey of US homes found that "most US homes have detectable levels of dust mite allergen". A UK PubMed study found similar levels of infestation, noting that "factors such as older homes, carpets, and mattresses, damp and condensation are associated with higher mite allergen".

By stabilizing relative humidity at an optimum level of under 50%, dehumidifiers play a crucial role in reducing dust mite infection, PubMed research has established. The impact is massive, with researchers noting allergen levels were ten times lower in homes that used a dehumidifier.

If you have children, a dehumidifier could help reduce the risk of them developing a range of conditions, such as asthma, allergic rhinitis, atopic dermatitis, and abnormal lung functions, one World Allergy Organization Journal study found.

Do dehumidifiers help with asthma?

Dust mites are the main trigger for asthma, says the American Lung Association. So reducing them is, understandably, one of the main priorities, says the Nursing Clinics of North America.

The evidence is clear that dehumidifiers can reduce the risk of dust mite infection in your home, making the air better to breathe for those with asthma, but that’s not their only benefit.

High humidity can affect asthmatics in several ways, Healthline warns, causing trouble breathing or shortness of breath, coughing, tightness in the chest, and wheezing. These can cause your body temperature to increase, which can lead to dangerous symptoms such as dehydration. Together, this could lead to potentially hazardous asthma attacks, according to the AAFA. Dehumidifiers remove excess moisture from the air making breathing easier for everyone. Left on all night, they can also help improve sleep (whether you have asthma or not!).

Excessive moisture can also encourage mold growth, which can generate an allergic reaction and cause asthma attacks, says the NHS. Children are particularly susceptible to mold, with one PubMed study finding that children in moldy homes are three times more likely to develop asthma by the age of seven than others.

Mold can grow anywhere the humidity level exceeds 60%, says the EPA. So it’s important to limit moisture in the home, with a dehumidifier providing the first line of protection.

As well as dust mites and mold, humidity and air pollution are closely linked, says the AAFA. Whether you call it smog, ozone, or air pollution, a dehumidifier – specifically one fitted with a HEPA – can improve indoor conditions.

• Related: Does a dehumidifier cool a room?

Do dehumidifiers help with eczema?

Excessive sweating caused by high health and humidity can aggravate eczema, making skin feel itchy. So, do dehumidifiers help with eczema? Yes, but only in certain circumstances.

A dehumidifier can reduce moisture, making the indoor environment feel more comfortable. According to Everyday Health, less moisture means less irritation. To have the maximum impact, you should operate your dehumidifier alongside an air conditioning system to reduce the temperature and humidity.

Those with eczema can find that dry air with low humidity can make symptoms feel worse, according to the National Eczema Association. The problem can be exacerbated in winter, as we turn on heating systems, we dry out the air even further. In these situations, a dehumidifier could actually make things worse by removing further moisture from the air. If you suffer from eczema and recognize this as a trigger, consider investing in a humidifier to provide additional moisture to the air when it’s needed.

Wondering what causes allergies and if there's a cure? Well, allergies are exaggerated immune reactions to foreign substances. They can cause many physical symptoms that depend on the degree of immune response and the mode of entry into the body. 

The global prevalence of allergies is rising and about 30-40% of the world's population may have a specific allergy, according to the patient advocacy group, the Global Allergy & Airways Patient Platform. Allergies can affect all age groups and may be triggered in response to common things such as foods, drugs, plant or animal products.

People with allergies may develop a skin rash, swelling and congestion of the upper airway when exposed to pollen or dust. In this article, you'll learn the causes of allergies and how you can manage them at home, including measures such as using the best air purifiers and decreasing exposure to the thing you're allergic to. 

How do allergies start?

According to Medical News Today, allergies are caused by allergens, which are foreign substances that are not usually harmful except in people with the genetic predisposition to mount an exaggerated immune response.

Allergens stimulate the immune system to produce a specific slew of antibodies (proteins that bind specific substances). These antibodies in turn trigger the release of chemicals such as histamines from mast cells. The combination of these chemicals produces physical symptoms such as itching, swollen eyes, red eyes, etc. that allergy sufferers complain about. For instance, the most common food allergies are mediated by IgE antibodies, according to a study published in 2016 in the journal Nature Reviews Immunology.

The type of allergen and the mode of entry into the body determine the physical external manifestation of allergies. For instance, exposure to skin allergens results in itchy skin rash, swelling and a burning sensation in the skin, while pollen allergens can cause a runny nose, chest tightness and difficulty breathing.

Here are some common allergens, according to Healthline:

• Food: Peanuts, eggs and shellfish
• Drugs: Penicillins, sulfur-containing drugs
• Stings from insects like bees, wasps
• Plant products such as pollen from grasses and trees
• Animal materials such as pet dander

A person may be hypersensitive to one or more of these allergens which may result in anaphylaxis — a life-threatening allergic reaction due to excessive immune system response to a specific allergen.

Anaphylaxis is characterized by low blood pressure, difficulty breathing and severe skin reactions, according to the Mayo Clinic. It is a medical emergency and requires prompt hospital treatment.

Can allergies be cured?

There is no cure for allergies, children can outgrow some food allergies that they develop in early childhood, according to a 2014 survey conducted by the Immunology and Allergy Clinics of North America. The study showed that children who were initially allergic to milk in early childhood became milk-tolerant later. Some children also outgrow early childhood allergies to foods like eggs.

Allergies can be managed using multiple methods, but one of the most effective ways, as revealed by a study in the journal Adolescent Medicine, is to identify your allergens and avoid exposing yourself to them. 

Here are some tips to decrease exposure to home allergens, according to Healthline:

• Install dehumidifiers to reduce damp surfaces at home.
• Replace rugs with ceramic tiles for floors.
• Decrease exposure to pets.
• Install HEPA filters to remove airborne allergens.

Medications such as antihistamines are effective against itching, runny nose and skin swelling, according to the Mayo Clinic.

Individuals who are severely allergic to airborne allergens may need allergy shots. These allergy shots contain a weak form of an allergen injected into the body to train the immune system to mount an immunologic response when exposed to the allergen later.

For instance, in people with pollen allergies, a small concentration of a pollen allergen is injected into the body to train the immune system to create antibodies against that substance. During subsequent exposure to pollen, these already-made antibodies eliminate pollen before the rest of the immune system can be activated. A review study on the efficacy of allergy immunotherapy for control of asthma conducted at the University of Edinburgh, showed allergy shots are capable of reducing asthmatic symptoms but there were associated adverse reactions. Therefore, the risk and benefit are considered before an allergy immunotherapy is administered – preferably by a specialist.

Can allergies cause a sore throat?

Allergies cause a sore throat when airborne allergens stimulate the immune cells in the nose. This leads to an immune response that results in the production of thick mucus and secretions in the nasal cavity. This results in post-nasal drip, or an itchy or irritating feeling associated with throat pain as the thick mucus flows down from the back of the nasal cavity into the throat. Postnasal drip may also come with nasal itching, congestion, eye swelling, sneezing or coughing. 

Allergies vs COVID-19: What's the difference?

Allergies and COVID-19 may share common features and symptoms such as a cough and nasal congestion, but there are some subtle differences between them. However, if you do have symptoms consistent with allergies, it is critical to be tested for COVID-19, as many of the symptoms overlap, and you may unwittingly spread the deadly coronavirus if you assume your symptoms are caused by allergies.

The following factors differentiate allergies from COVID-19, according to the Mayo Clinic:

Causative agent: COVID-19 is caused by the SARS-COV-2 virus. Infectious organisms do not cause allergies.

Mode of transmission: COVID-19 is transmitted when an infected person releases infectious respiratory droplets when, sneezing, coughing, talking or breathing, according to the Centers for Disease Control and Prevention (CDC). In contrast, allergies are not contagious and the respiratory droplets from an allergic person do not contain any infectious organism. 

Clinical Symptoms: According to the CDC, COVID-19 triggers symptoms like fever, shortness of breath, muscle aches, and loss of smell and taste, which are typically absent in allergies. Note: anaphylaxis can cause difficulty breathing. By contrast, allergy symptoms such as persistent itching and watery eyes are not associated with COVID-19.

Treatment: While allergies are treated using medications and prevention measures like avoiding allergy triggers, the single best way to prevent COVID-19 is to get vaccinated against the disease.

What causes allergies: The round-up

Allergies are caused by allergens, and they can be found in some foods, airborne particles, drugs, animal dander, etc.

Allergy symptoms are easy to manage with medications and preventive measures to avoid allergens. Seek a doctor's counsel and clinical evaluation if you are prone to allergies.

Spring and summer are fun for some and terrifying for others because it marks the onset of lots of allergy season symptoms. 

These two seasons are associated with allergy trouble because the many pollens and spores from trees and grasses are airborne and can trigger allergy symptoms. Allergy season differs for everyone due to their location and the seasonal trees and specific pollens in the air where they live and work. For instance, ragweed pollen is more prevalent in the fall months, so people sensitive to this particular pollen will only develop allergy symptoms in the fall.

The Centers for Disease Control and Prevention (CDC) states that 19.2 million adults and 5.2 million children reported hay fever symptoms in the United States in one year. These figures indicate that allergy season symptoms are common across all age groups.

Seasonal allergy symptoms include wheezing, itching, runny noses and swollen, irritated eyes. They often require close monitoring by a medical professional for accurate diagnosis and to prevent severe immunologic response in susceptible individuals.

In this article, Dr. Christopher Oseh, an experienced primary care physician, explains the characteristics of common allergy season symptoms and how to manage them with measures such as using the best air purifiers, remaining indoors or using nasal sprays. In a separate article, Doctor Oseh explains what causes allergies. 

Common allergy season symptoms

Allergy season symptoms manifest in various ways and degrees depending on an individual’s immune system sensitivity. Drugs help to relieve some of these symptoms, while others may require avoiding exposure to the triggers. An individual with hay fever may have one or more of these symptoms.

1. Itching

Itchiness occurs when mast cells, a type of white blood cell in your body, release a chemical called histamine. Itching can be localized in specific areas like the eyes, nose, or skin, or generalized, depending on the region of the body exposed to an allergen.

2. Dry cough

Throat irritation from postnasal drip causes a characteristic dry cough correlated with allergies. Postnasal drip is the flow of accumulated fluid and mucus from the back of the nasal cavity down into the throat. 

3. Wheezing

Wheezing is a whistling sound heard most often in asthmatics or those with hypersensitive airways. The inflow of respiratory allergens causes the release of fluids and mucus that accumulates and blocks small airways in the lungs.

4. Runny nose

Inhaled airborne allergens trigger the production of fluids in the nose that accumulates and drains out of the nose. The nasal secretions are often clear but may appear mucoid. 

5. Sneezing

This is a reflex response because of foreign bodies like pollens, dust, and other air particles in the nose. Sneezing serves as a defense mechanism to expel inhaled airborne allergens, which are nasal irritants.

6. Swollen eyes

Allergens exposed to the eyes stimulate a local inflammatory reaction together with tissue swelling in the eyes. In some people, this may be associated with teary eyes, which is the body’s way to flush out foreign particles in the eyes. 

7. Sore throat

Inhaled allergens cause the production of fluid and thick mucus, which collects in the nose and flows down into the throat, leading to throat pain. 

8. Red eyes

The local inflammatory reaction in the eyes increases blood flow, which appears as eye redness and eye discomfort.

9. Headaches

A classical dull headache may occur when inflammatory fluid and mucus block nasal sinuses, which are air spaces in the skull.

How to treat allergy season symptoms

The Asthma and Allergy Foundation of America (AAFA) states that allergy season treatment requires a multi-dimensional approach and depends on the presence of medical conditions such as asthma or chronic obstructive airway disease (COPD), both of which affect symptom severity. Different classes of drugs are used for allergy treatment, and the region of the body affected determines the route of drug administration. For instance, nasal congestion requires local therapy like nasal sprays, while anti-inflammatory eye drops treat allergy-induced eye swelling. We've also investigated whether air purifiers help with allergies.

Is it possible to prevent allergy season symptoms?

Use the following methods to avoid allergens or reduce exposure to them:

• Wear a pollen mask to avoid exposure to pollen
• Remain indoors during stormy days
• Avoid crowded rooms
• Cover your nose when someone close to you coughs or sneezes
• Install air purifiers to filter out airborne particles in your house
• Use warm saline to wash out inhaled airborne particles in your nose

Medication for allergy season symptoms

Antihistamines: These drugs block the effects of histamines in the tissue and help stop itchy symptoms irrespective of the location in the body. A study conducted to assess the efficacy of oral antihistamines in urticaria (allergic skin disease) revealed a significant improvement in the symptoms among subjects treated with antihistamines.

Corticosteroids: These are anti-inflammatory drugs that reduce inflammatory reactions, especially swelling in the body, locally or generally. Corticosteroids are available in various forms, such as nasal sprays, oral tablets, and creams. Nasal corticosteroids are sprays used to reduce nasal tissue swelling. 

Doctors prescribe oral corticosteroids to reduce generalized inflammatory responses in the body and the creams are for skin reactions.

Another study conducted on the effect of intranasal steroids for relieving hay fever symptoms showed an improvement of these symptoms in study participants administered intranasal steroids.

Nasal decongestants: These are nasal sprays used to relieve nasal congestion due to fluid and mucus accumulation. Nasal decongestants are used for a maximum of three days because more prolonged use may increase the risk of nasal swelling due to rebound effects.

Mast cell stabilizers: This class of drugs prevents mast cells from releasing histamine, which causes local or generalized itching.

Allergy immunotherapy: This therapy entails the administration of specific allergens into the body with the aim of reducing the hypersensitivity response of the immune system. This requires the administration of allergy shots to individuals regularly over time to desensitize them to a particular allergen. Allergy immunotherapy is used only in severe allergies or when medications alone do not control symptoms. Allergy immunotherapy is best done before allergy season begins to prepare the immune system. 

Allergy season symptoms present differently in each person. These symptoms can be non-specific and may cause life-threatening reactions like anaphylaxis, so it is essential to seek a medical doctor’s help for professional evaluation and counsel.

• Read more: What is the air quality index?

Air purifiers clean the air in a room by drawing in the air, trapping the airborne pollutants within it, and then pushing filtered, clean air back into the space. Some of these airborne particles, such as pollen, pet dander and mold spores, are irritants that can aggravate people's allergies. These particles can make their way into our bodies as we breathe, causing runny noses, watery eyes and other adverse reactions in people who are sensitive to the allergens.

So do air purifiers help with allergies? In short, yes they can, but only to a certain extent.

Air purifiers can be effective at trapping the small particles that trigger allergies, preventing them from circulating in the air and then being inhaled. However, these devices are not a complete solution, Dr. Payel Gupta, an assistant professor at the SUNY Downstate Medical Center in New York and a national spokesperson for the American Lung Association, told Live Science by email. "Each device has its limitations, and individual responses can vary," she said.

Aneta Ivanova, a pediatric allergy nurse consultant for the Sandwell & West Birmingham Hospitals NHS Trust in Birmingham, England, agrees with that statement.

"Air purification is often recommended as a component of environmental improvement for patients with allergic respiratory disease, but there is little medical evidence to support that air purifiers help directly to significantly reduce allergies or respiratory symptoms," Ivanova said. "There is a need for larger randomized control trials to be able to scientifically prove the true effectiveness [of these devices]," she said. (Randomized controlled trials include a placebo group, for comparison, and can provide direct evidence that an intervention relieves specific symptoms.)

• Related: What causes allergies?

Historically, the studies that have been conducted have suggested that air filtration can help ease some of the symptoms of hay fever, such as sneezing, nasal congestion and watery eyes. However, but it does not appear to significantly improve people's lung function, boost their quality of life or reduce their need for allergy medications, according to a 2024 analysis published in the journal Indoor Air.

These mixed findings may partially stem from the limitations of the studies. For instance, air purifiers tend to be tested under carefully controlled conditions in laboratories, rather than in real-world scenarios. Factors such as the location of the purifier, its flow rate and its operating time will also affect how well it reduces allergy symptoms, so there may be some discrepancies between studies.

Different filters within air purifiers might also alter their effectiveness. Most of the best air purifiers on the market are equipped with High-Efficiency Particulate Air (HEPA) filters, which according to the United States Environmental Protection Agency (EPA) can remove up to 99.97% of dust, pollen and airborne particles measuring 0.3 microns across from the air. These filters consist of a multilayer network of very fine fiberglass threads — thinner than strands of a human hair.

"HEPA filters are particularly effective at trapping airborne particles, including some of the common allergens," Gupta said.

For example, air purifiers equipped with HEPA filters were found to be more effective than HVAC systems (Heating, Ventilation and Air Conditioning units) at filtrating airborne particles as small as 2.5 microns, according to a 2025 study published in the Journal of Exposure Science & Environmental Epidemiology. For 12 months, scientists monitored air pollution levels in 99 school classrooms with HEPA filter air purifiers and 87 school classrooms with HVAC systems, and found that the levels of airborne particulates were on average 39.9% higher in classrooms equipped with non-HEPA air cleaners.

Ultimately, though, "while air purifiers can provide benefits for managing allergies, asthma and exposure to pollution, they are most effective when combined with good indoor air quality practices, such as regular cleaning, moisture control and proper ventilation," Gupta said. An air purifier, alone, may not do the trick.

This article is for informational purposes only and is not meant to offer medical advice.

The source of allergy trouble ranges from pet hair and dander to dust and pollen, resulting in sneezes, wheezing, and rashes - but do humidifiers help with allergies? The symptoms of allergies are common, with nearly a sixth (50 million) of the US population suffering from some type of reaction. 

In this feature, we'll look at what a humidifier is and the science behind how they add moisture to the air. But it's important to understand that humidifiers won't serve the job of an air purifier, which works to capture allergens, dust, and even viruses. We have a whole feature on air purifiers vs humidifiers to help you understand the key differences.

• Related: Best humidifiers

How can humidifiers help with allergies?

A humidifier is an electronic device that pumps moisture into the air. When the humidity in a room is too low or too high, it can trigger allergy symptoms, especially when you're dealing with dust, pollen from open windows, or indoor pets. You can place a humidifier in any room or enclosed space of your home. Simply stated, humidifiers work by creating moisture and filtering dust, dander, and virus particles from the air. 

Now that we're spending a larger chunk of our time indoors, it's more important than ever to create a safe environment to eat, sleep, work, and live in. And humidifiers help to do just that. Too little humidity causes inflamed, irritated nasal passages, rashes, and dry skin, and too much creates an environment ripe for bacteria, dust mites, and molds, all of which can affect your health. It can contribute towards something called sick building syndrome, which we deal with in our related investigation.

How do humidifiers work?

Humidifiers work by adding temperature-regulated moisture to the air inside your home. You pour water into the humidifier’s reservoir, and it outputs a gentle, filtered mist. The filters inside the unit have an antimicrobial surface that helps prevent the growth of mold, algae, fungus, and bacteria. 

Humidifiers are great machines, but they won't cure allergies. However, the right humidity level in the home can help improve symptoms and make allergies less of a nuisance. A study by the Clinical research center shows that the optimum level of moisture for home humidification is between 40-50%. Remember, when the humidity level is too high, it encourages mold and dust mites, and low levels aggravate the sinuses, skin, and lungs. So it's crucial to get the level correct. On a hot, humid day, when you have the windows open, it's unlikely a humidifier will offer any benefit. If you have the air conditioner running or it's the middle of winter, though, a humidifier can soothe tender sinuses.

How can humidifiers help with allergies?

If you have pets, you'll want to pay special attention to your home's humidity. When moisture levels are high, pet dander sticks to surfaces, which you can then pick up on clothing and skin. Proper humidity at ideal temperatures fixes that and can help clear stuffy noses and tickling throats, too. 

Other allergies, such as eczema, can also be kept under tighter control with a humidifier. The National Eczema Association reveals that the key to treating and preventing eczema outbreaks is to keep the skin’s moisture intact. Low temperatures and dry air, especially in the winter or air-conditioned rooms, can aggravate the skin and leave it sore and inflamed.

A higher level of humidity can also help eliminate viruses in the home. One research study tested how flu particles changed in the air when humidity levels reached 40%. The results showed virus particles were deactivated, making them less infectious when circulating in humidified air. Air purifiers can help with allergies too, so think about what you need when choosing your in-home air quality devices.

One important note: it's of the utmost importance you keep your humidifier clean. You'll need to change the filter regularly and clean the water tank to prevent waterborne bacteria from forming, which is the last thing you need when you're already suffering from itchy, runny eyes and noses.

• Related: What is the air quality index?

What types of humidifier are there?

There's no shortage of humidifiers on the market, and they come in all shapes and sizes. Here are the main types and how they work to humidify the air.

• Evaporators: This style of humidifier sucks in air, passes it through a filter, and then fans the hydrated air back out.
• Steam vaporizers: This humidifier creates steam internally, cooling it to an appropriate temperature before pumping it into your living space.
• Ultrasonic humidifiers: Typically smaller and more high-tech, these humidifiers use vibrations to vaporize water and pump steam back into the air. 
• Whole house: These humidifiers attach to your central air conditioning or heating system, eliminating the need to purchase small units for each room.

Other ways to improve your home’s air quality

There are numerous other ways to clean the air in your home and minimize allergy symptoms. The NASA Clean Air Study showed that many house plants filter airborne irritants through their root system and can scrub the air in your home to some degree. Plants like English ivy, spider plants, peace lilies, and bamboo palms filter the air around them, removing toxins and particles.

Other inexpensive and simple ways to help with allergies in the home include keeping a small window open for ventilation, cleaning and dusting often, and brushing and bathing pets regularly. Indoor plants improve air quality too, and they look nice - just make sure they won't have an adverse effect on your pets!

• Read more: 9 allergy season symptoms to look for

A man's persistently runny nose following a COVID-19 test wasn't caused by allergies as he suspected, but rather cerebrospinal fluid leaking from his brain, according to a new report.

The man, who lives in the Czech Republic, received a COVID-19 nasal swab test in March 2020 after he had contact with a person infected with COVID-19, according to the report, published Thursday (Sept. 9) in the journal JAMA Otolaryngology–Head & Neck Surgery. The man's test was negative, but afterward he experienced a runny nose from just his right nostril. This symptom, which the patient mistakenly thought was due to allergies, lasted for months before he went to see a doctor in December 2020.

A CT scan of his skull showed that the man had an injury to the cribriform plate, a spongy bone that separates the nose and the brain. He was diagnosed with a cerebrospinal fluid (CSF) leak, a rare but serious condition in which the clear fluid that surrounds the brain and spinal cord leaks through a defect in the skull and out through the nose, according to Johns Hopkins University. Typically, the leakage happens from just one side of the nose, according to the Cleveland Clinic.

CSF leaks are dangerous because they can increase the risk of meningitis, which is an infection of the membranes that surround the brain and spinal cord. Still, patients can have a CSF leak for years before they develop serious problems, Live Science previously reported. 

Related: 10 things you didn't know about the brain

CSF leaks can have a number of causes, including head injury or brain or sinus surgery. In this case, the man's CSF leak was likely an extremely rare complication caused by his March 2020 COVID-19 test. The man had received a nasopharyngeal COVID-19 test, in which a healthcare provider takes a sample from deep inside the nose, where the nasal cavity meets the upper part of the throat, according to the Food and Drug Administration. Such tests are known to be uncomfortable, and they have been referred to as "brain scrapers." However, although these tests may feel strange and result in symptoms such as watery eyes,  they shouldn't be painful, according to the Virginia Department of Health.

What's more, although the nasopharyngeal test was the main testing method used early in the pandemic, such tests have become less common following the development of other tests that can detect COVID-19 using samples collected from the front part of the nose, according to The Conversation.

It's also important to note that only a handful of CSF leak cases linked with COVID-19 tests have been reported worldwide since the pandemic began, out of the hundreds of millions of COVID-19 tests conducted. In the Czech Republic, 25 million COVID-19 tests were conducted between March 2020 and May 2021, according to the JAMA report. (In the U.S., more than 539 million tests have been conducted since the pandemic began, according to data from the Centers for Disease Control and Prevention.)

Two previously reported cases of CSF leaks tied to COVID-19 testing were in people who had existing defects in their skull base, which increased their risk of this complication, the report said. In one of those cases, described in the April 2021 issue of the Journal of Clinical Neuroscience, the authors believe that the nasal swab was also "inserted at an incorrect angle." 

The new report appears to be the first case of a CSF leak following COVID-19 testing in which the patient didn't have a preexisting skull defect. A CT scan performed on the man in 2011 showed no defects, the JAMA report said.

The man needed surgery to close the cribriform plate injury, along with a prescription for antibiotics to prevent infection. The man recovered well without complications from his surgery, but at a follow-up appointment three weeks later, he reported that he could not smell out of his right nostril, the report said.

Originally published on Live Science.  

Calls to emergency departments spiked in the wake of a thunderstorm that swept over Melbourne, Australia, in 2016. It was a rare outbreak of "thunderstorm asthma," the most severe ever recorded. 

Now, a new model, published April 14 in the journal PLOS One, hints that a combination of lightning strikes, wind gusts, low humidity and popping pollen grains may be to blame for the surge of asthma attacks following the storm, which contributed to the deaths of 10 people. 

As the name suggests, thunderstorm asthma outbreaks occur when a passing storm disperses allergen particles in the air, triggering asthma attacks in susceptible people, according to the American Lung Association. Those most at risk include: people with diagnosed asthma, particularly if their condition is poorly controlled; people with undiagnosed asthma; and those with seasonal hay fever or a rye grass allergy, according to a 2017 report from the Victoria State Government's Chief Health Officer. 

Related: Elves, sprites & blue jets: Earth's weirdest lightning 

Although thunderstorms rumble through the sky fairly frequently, thunderstorm asthma events are quite rare. Since the first recorded thunderstorm asthma event in 1983, 22 accounts of the phenomenon have appeared in the medical literature, first author Kathryn Emmerson, a senior research scientist at Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO), told Live Science in an email. 

Of these 22 outbreaks, 10 occurred in Australia, so it seems the country is a "hotspot" for such events, she added.

The most severe outbreak to date occurred in the Melbourne area on Nov. 21, 2016, at roughly 5:30 p.m. local time. Leading up to the storm, the weather had been hot, above 86 degrees Fahrenheit (30 degrees Celsius) and very dry, Emmerson said. The air held more than 133.4 pollen grains per cubic yard (102 grains per cubic meter), indicating that grass pollen season had reached its peak in Australia. 

"The event occurred at the peak of the hay fever season, and most patients were suffering with an allergic response in their airways," Emmerson said. Normally, rye grass pollen grains — the main culprit behind the outbreak — are too large to reach the deep lungs and instead get caught in the nose and throat; but somehow, during the 2016 storm, the weather conditions broke down these grains into smaller particles, triggering asthma symptoms in a large number of people.

The storm pushed a wall of gusty wind through the region, but dropped very little rain, only about 0.03 to 0.15 inches (1 to 4 millimeters), according to a 2017 state government report. A wave of high humidity followed the storm, as well. But because of the sparse rain, many people remained outside as the storm passed by, which increased the number of people exposed to the pollen, Emmerson noted. 

That evening and the following day, local health care providers were suddenly inundated with a flood of patients seeking care for respiratory-related conditions. 

The public hospitals in Melbourne and nearby Geelong saw a 672% increase in patients arriving at emergency departments with respiratory problems, as compared with the average number for that time of year; that amounted to 3,365 more cases than expected based on the three-year average. Ambulance transport services, local primary care physicians and pharmacies were also bombarded with calls regarding emergency medical care. And in the end, storm-related asthma symptoms contributed to the deaths of 10 people, according to the state coroner.

Of course, the big question is, why did this disaster occur? In the past, scientists theorized that downdrafts of cold air from the storm clouds stirred up grass pollen grains below, pushing them skyward; once captured inside the clouds, the pollen grains became saturated with water and began to burst, so the theory goes. A 2016 study, published in the Journal of Applied Meteorology and Climatology, supported this idea, noting that wind in the clouds also contributes to the pollen-grain-popping, as well as lightning, to a lesser extent.

Related: Cloud in a bottle - Science fair projects

Following the Melbourne outbreak, the state health department wanted to create some sort of forecasting system to help predict when another outbreak might strike. Emmerson and her colleagues went to work crafting this forecast system but found that high humidity, supposedly the main driver of pollen grain ruptures, wasn't a helpful predictor for thunderstorm asthma events. 

We "found that conditions of high humidity, a measure of how much water is in the atmosphere, occurred almost every evening — not what you want from a warning system predicting a relatively rare event," Emmerson said. So if high humidity served as the basis of their warning system, it might set off too many false alarms. To craft a better forecast model, Emmerson and her team looked for other atmospheric conditions that might set the stage for outbreaks of thunderstorm asthma. 

Using data from the 2016 event as a guide, the team crafted computer models to test how airborne pollen grains rupture under different weather conditions; they backed up these models with lab experiments, in which they subjected pollen grains to wind gusts and electrical pulses. Based on their experiments and models, they found that several phenomena work in tandem to smash the grains to bits, namely, strong winds, lightning strikes and the build-up and discharge of static electricity brought on by low humidity, as seen just before the 2016 storm.

But notably, "the lightning method was the only mechanism to generate a pattern in [sub-pollen particles] following the path of the storm," the authors wrote. Assuming the 2016 storm had a similar pollen-laden tail, this may somewhat explain the timing and distribution of emergency calls for ambulances that occurred during the event, hinting that lightning strikes may be a key trigger for thunderstorm asthma. 

However, during the fateful storm, not much lightning struck within Melbourne itself, where most of the asthma attacks occured, but instead fell to the east and south of the city, the Australian news outlet 9News reported. So while there seemed to be some correlation between the lightning strikes and asthma attacks, it wasn't a perfect explanation. 

In fact, "none of the tested processes completely satisfied our requirements for a warning system," meaning none stood up as a wholly reliable signal for forecasting thunderstorm asthma events, Emmerson told Live Science. "We haven't fully cracked the code on the triggers of thunderstorm asthma yet." 

For now, the best approach for predicting such events is to monitor for thunderstorms associated with severe wind gusts, while also tracking the levels of unburst grass pollen in the air. Emmerson and her team plan to improve upon their current model, in part by better estimating the amount of whole and burst pollen grains higher in the atmosphere, close to the clouds.

Originally published on Live Science.

Imagine a woman has a few drinks one night, pops some ibuprofen in the morning for her hangover, and goes for a run. She's never had an issue with alcohol, ibuprofen or exercise before. But this time, some combination of the three triggers a life-threatening allergic reaction known as anaphylaxis.

This is a real case that happened to a patient of Dr. Andrew Murphy, an allergist at Suburban Allergy Consultants in Pennsylvania. So, is it possible to be allergic to exercise?

Not technically, Murphy said. When a person is exposed to something they're allergic to, a protein from the allergen, for example peanuts, grass or cat dander, interacts with antibodies on immune cells in their body. The immune cells fire off chemicals like histamine that cause sneezing, hives, wheezing and other symptoms. There's no protein that enters the body when a person works out, so it's not possible to be allergic to running. 

But, exercise can trigger the same array of symptoms in people with a rare condition called exercise-induced anaphylaxis. "It's not necessarily antibody-mediated, but exercise is a trigger and the allergy [immune] cells are still activated," Murphy told Live Science.

Related: Why do I get sore days after I’ve worked out?

Exercise alone is enough to trigger an allergic reaction in some people, but the way it does so is unknown. One theory proposes that exercise causes a release of endorphins, which triggers certain immune cells to release chemicals such as histamine, according to a 2010 review in the journal Current Allergy and Asthma Reports. 

Other people, like Murphy's patient, have a condition known as food-dependent exercise-induced anaphylaxis, or FDEIA. For them, eating a certain food before working out can cause symptoms such as wheezing or hives — even if they have no reaction to that food when lounging. In the case of Murphy's patient, the "food" was either alcohol, ibuprofen, or a combination of the two. There are several theories why certain foods in combination with exercise can cause an allergic reaction, including that working out makes the gastrointestinal tract more permeable, allowing allergens to come into better contact with the immune system. Ibuprofen can further increase permeability and the body's uptake of foreign allergens, and it may directly interact with immune cells, according to the review.

Exercise-induced anaphylaxis is rare. About 2% of people in the Western world experience anaphylaxis, and 5% to 15% of cases are exercise-induced, according to the review. The food-dependent version of the condition is less common and represents between a third and a half of all cases. Not many children come into the office with either condition, Murphy said, and it generally appears in teens and adults. 

Treatment for food-dependent exercise-induced anaphylaxis is simple: Don't eat for four hours before and after working out, according to a review in the journal Expert Review of Clinical Immunology. Another option is to avoid the triggering foods entirely, if those foods are known. 

When exercise is the sole trigger, managing the condition can be harder than managing FDEIA, but doctors can help patients develop specialized exercise regimens, Murphy said. The amount of exertion someone with the condition can do safely varies. A casual stroll can trigger a reaction in some people, but others can ride a bike with no issues. Each patient must work with a doctor to figure out their own limits. Murphy always prescribes an EpiPen in case of emergency, and antihistamines can help prevent episodes, according to a 2001 review in the journal American Family Physician.

Serious reactions in response to exercise are rare. In 25 years of practice, Murphy has only seen one person pass out from it. "I usually see more people with cutaneous [skin-related] symptoms like hives, or they have some lip swelling or get wheezing with it," he said.

Originally published on Live Science.

Moderna's COVID-19 vaccine rarely causes severe allergic reactions, according to new data released by the Centers for Disease Control and Prevention (CDC).

Between Dec. 21 and Jan. 10, more than 4.04 million people were given Moderna's COVID-19 vaccine, but only 10 developed a serious, potentially life-threatening allergic reaction called anaphylaxis. That works out to be around 2.5 cases of anaphylaxis per 1 million people vaccinated, according to the CDC's Morbidity and Mortality Weekly Report.

It's not yet clear what's causing the severe allergies, but nine out of 10 of these cases occurred among patients with previously known allergies (five previously had anaphylaxis). Most had

allergies to various medicines such as penicillin, but one had environmental and food allergies and another didn't have any prior known allergies, according to the report.

Related: 14 coronavirus myths busted by science

Nine out of 10 of the patients developed symptoms — such as vomiting, nausea, wheezing, tongue swelling and rash — within 13 minutes of getting the vaccine and one developed symptoms within 45 minutes.

All 10 patients were treated with epinephrine — a hormone also known as adrenaline that is the key ingredient in EpiPens and similar autoinjectors; four were treated in an emergency department and six were hospitalized, with four requiring intubation. But all 10 patients recovered, according to the report.

"Based on this early monitoring, anaphylaxis after receipt of Moderna COVID-19 vaccine appears to be a rare event," the authors wrote in the report. But because there's not yet widespread data on COVID-19 vaccines, it's difficult to compare the risk of anaphylaxis with non-COVID-19 vaccines, they wrote. In a previous Morbidity and Mortality Weekly Report, published on Jan. 15, researchers estimated that the Pfizer-BioNTech vaccine causes anaphylaxis in about 11.1 cases per million doses (0.001% chance); that estimate was based on early data.

Still, both the anaphylaxis associated with both Pfizer's and Moderna's COVID-19 vaccines seems to be above the average number of anaphylaxis cases found for previous vaccines. In 2015, researchers calculated that the chance of developing a severe allergic reaction to a vaccine is about 1.31 in 1 million, according to a 2015 study published in the Journal of Allergy Clinical Immunology. "True allergic reactions to vaccines are very rare," Dr. Purvi Parikh, allergist and immunologist at NYU Langone Health, previously told Live Science. "Statistically, you're more likely to be hit by lightning than have a true anaphylactic reaction to a vaccine." Though the cases are extremely rare — and should not dissuade people from getting the vaccine — experts are working on identifying what could be causing the allergies. 

People who have had an allergic reaction to the first dose of the vaccine should not receive the second dose, the authors wrote. Vaccine centers should have all the necessary supplies and trained staff to treat anaphylaxis, they wrote. The CDC also recommends that people who receive COVID-19 vaccines should also be monitored for about 15 minutes, or 30 minutes if they have a history of allergies or anaphylaxis.

Originally published on Live Science.

Stepping out of a hot shower into a cold bathroom almost killed a Colorado man, who had developed a serious allergic reaction to cold temperatures.

The 34-year-old old man collapsed after getting out of the shower, and his family found him on the floor, according to a report of the case published Oct. 27 in The Journal of Emergency Medicine. The man was struggling to breathe and his skin was covered in hives. He was experiencing a life-threatening, whole-body allergic reaction known as anaphylaxis.

When paramedics arrived, his family told them that the man had a history of being "allergic to the cold weather," according to the report. He had previously experienced hives as a reaction to the cold, but not anaphylaxis. These episodes started after he moved from Micronesia, which has a tropical climate, to Colorado, which sees colder temperatures, the report said.

Related: The 9 weirdest allergies 

Paramedics treated the man with epinephrine and oxygen, and rushed him to the emergency room. When he got to the hospital, he was sweating profusely and had hives all over his body.

Doctors diagnosed him with cold urticaria, an allergic reaction of the skin after exposure to cold temperatures, including cold air or cold water, according to the Mayo Clinic. People can also develop symptoms after consuming cold food or drinks, Live Science previously reported.

The most common symptom is a red, itchy rash (hives) after exposure to the cold; but in more serious cases, people can develop anaphylaxis, which can cause their blood pressure to plummet and airways to narrow, making breathing difficult. These more severe reactions typically occur with full-body skin exposure to the cold, such as when people swim in cold water, the Mayo Clinic says. In the man's case, his entire body was exposed to cold air after stepping out of his shower. 

Doctor's confirmed the man's diagnosis using an "ice cube test," which involves placing an ice cube on the skin for about 5 minutes. If the patient develops a raised, red bump on the skin where the ice cube was, they are diagnosed with cold urticaria.

Exactly how common the condition is overall is not known — one study in Europe found a prevalence of 0.05%, according to the National Institutes of Health. Anaphylactic reactions are less common than hive-like reactions.

In most cases, the cause of the condition is not known, but sometimes it can be inherited, meaning people have a genetic predisposition. In other people, cold urticaria is triggered by something that affects the immune system, such as a viral infection or certain cancers.

The allergic reaction happens because exposure to the cold causes the immune system to release chemicals called histamines, which trigger an inflammatory response, Live Science previously reported.

At the hospital, the man was treated with antihistamine and steroids, and his condition improved. Before he left the hospital, he was counseled to avoid exposure to cold water or other situations in which his whole body would be exposed to the cold. He was also prescribed an epinephrine auto-injector, which can treat anaphylaxis in emergency situations.

Originally published on Live Science. 

The National Institutes of Health (NIH) has launched a new study to determine the rate of COVID-19 infection among U.S. children.

The study, known as the Human Epidemiology and Response to SARS-CoV-2, or HEROS, will recruit  6,000 people from 2,000 U.S. families located in 11 cities, according to a statement from the National Institute of Allergy and Infectious Diseases (NIAID). The participants will be pooled from other NIH-funded pediatric research studies, in order to expedite recruitment, and will include healthy children and children with asthma or other allergic conditions. 

The research team will monitor each child and their family for six months to track who catches COVID-19, whether the children transmit the virus to other family members and which family members ultimately develop symptoms. 

Related: 11 (sometimes) deadly diseases that hopped across species 

"One interesting feature of this novel coronavirus pandemic is that very few children have become sick with COVID-19 compared to adults," NIAID Director Dr. Anthony Fauci said in the statement. "Is this because children are resistant to infection with SARS-CoV-2 [the virus that causes COVID-19], or because they are infected but do not develop symptoms?" 

The HEROS study could help fill critical gaps in knowledge by investigating how COVID-19 manifests in children, Dr. Tina Hartert, lead researcher of the HEROS study, added in the NIAID statement. 

"So far, data on the extent of SARS-CoV-2 infection in the U.S. population have been limited to people who physically interact with the health care system: those who are tested — especially those who test positive — and those with severe disease," Hartert said. While somewhat valuable for guiding public health policies, these data do not "enable us to understand the full extent of SARS-CoV-2 infection in the entire population," she said.  

For instance, preliminary data from an NIAID-funded study, published online April 22 in the Journal of Allergy and Clinical Immunology, suggest that children and adults with respiratory allergies, asthma or a sensitivity to allergens may harbor fewer ACE2 receptors in their airways. The coronavirus SARS-CoV-2 exploits ACE2 receptors as a doorway into cells, so theoretically, people with fewer ACE2 receptors may be less likely to contract a severe infection than people with large quantities of these receptors, the authors speculated. By including children with and without allergies, the HEROS study may help determine how allergies and asthma relate to COVID-19 risk.   

The HEROS study will be conducted remotely, so a caregiver in each child's household will be tasked with collecting nasal swab samples from the primary study participant and other enrolled family members every two weeks. Along with collecting swab samples, the caregiver will complete online questionnaires about each participant's symptoms, social-distancing practices, activities outside the home and exposure to people who are sick. 

If any member of the household develops symptoms of a possible viral infection, the family will complete a special questionnaire to determine whether the illness is likely to be COVID-19. If so, the infected person will be asked to supply a stool sample within 24 hours, and the designated caregiver will also collect additional nasal swabs from every member of the household. The nasal swabs and stool samples will be screened for the presence of SARS-CoV-2, and any airway cells collected in the process will also undergo genetic analysis.

The caregiver will also collect blood samples from participants at two weeks, 18 weeks and 24 weeks after study enrollment, as well as three weeks after the first likely case of COVID-19. They will collect blood samples "using a new, nearly painless device that extracts a small quantity of blood through the surface of the skin," the NIAID statement said. The blood will be screened for antibodies "once an appropriate antibody test becomes available," the statement added.

•  Can antibody tests tell if you're immune to COVID-19? 
•  The 12 deadliest viruses on Earth 
•  Top 10 mysterious diseases 

Originally published on Live Science. 

As the weather warms and pollen begins its dance across the sky, some people's bodies hurl them into a storm of watery eyes, runny noses and sneezing fits.

But sometimes the spring and summer months also bring bouts of tiredness. Can people with allergies also blame this on seasonal allergens? The answer is yes; there are several ways that seasonal allergies can make us feel low on energy.

An allergy or allergic reaction is, by definition, a fight that the body puts up when it's faced with a foreign invader, such as pollen, said Dr. Kara Wada, an allergist and immunologist at The Ohio State University Wexner Medical Center. [Can You Learn Anything While You Sleep?]

"The body expends a lot of energy in making all of the cells, proteins and all of the other substances" that build up during an allergic response, also known as inflammation, she said.

This energy expenditure wears out the body and "some of the same chemical signals … in addition to fighting off what it sees as an enemy, makes you feel unwell" and rundown, she said. This effect in seasonal allergies is like a watered-down version of the extreme tiredness that can overtake people who eat something they're allergic to.

Allergies can also indirectly cause you to feel tired by robbing you of sleep. "It's not uncommon to hear that people have poorer quality sleep from their allergies," Wada told Live Science, especially "if their nose is so stuffed up they have to breathe from their mouth or [if] post-nasal drip wakes them up in the middle of the night."

Why exactly do allergies make sleeping challenging? In essence, the body fights what it deems as foreign substances in the body by sending its little molecular army to the site of the invasion, causing inflammation there. Inflammation or swelling of the lymphatic tissue behind the nose, called the adenoids, could lead to a person breathing with their mouth open, which, in turn, can disrupt sleep, said Dr. Gloria Riefkohl, a pediatrician at Nicklaus Children's Hospital in Miami.

This disruption happens because when the adenoids get larger, they can cause obstruction in nasal passageways, which can reduce the amount of oxygen we need to breathe comfortably, said Dr. Priyanka Seshadri, a pediatric resident also at Nicklaus Children's Hospital.

"Seasonal allergies can definitely also affect concentration," she said. "Kids could be misdiagnosed with ADHD [attention-deficit/hyperactivity disorder] or a learning disability when sometimes it is just really bad allergies."

"Especially if you're not getting good quality sleep, we know that that can result in not as clear thinking, not as much focus," Wada said. "That's not going to lead to being your best self [while trying to work]."

Finally, people can become drowsy while trying to cure their allergies. The most common allergy-fighting medications are called antihistamines (histamines are a chemical the body releases during allergic reactions). But a common side effect of some of these medications, such as diphenhydramine (brand name Benadryl), is drowsiness, Riefkohl said.

• Booze Snooze: Why Does Alcohol Make You Sleepy, Then Alert?
• Why Are Pollen Allergies So Common?
• Why Do People Get Sick When the Seasons Change?

Originally published on Live Science.

The medicines you take contain a soup of active and inactive ingredients.

Active ingredients are the ones that provide a therapeutic benefit, while inactive ingredients are just that — inactive — meaning they don't react in the body and are instead there to enhance the properties of the medication itself, such as its taste, appearance and ability to be absorbed by the body. [7 Bizarre Drug Side Effects]

But it turns out that inactive ingredients may not be as, well, inactive as we think: A new study finds that, in some patients, inactive ingredients can trigger allergic reactions or other symptoms of food intolerance.

The study was published today (March 13) in the journal Science Translational Medicine. (Of note, three of the study authors hold a patent on a system that examines the burden of inactive ingredients in pills.)

The researchers began looking into inactive ingredients after senior study author Dr. Giovanni Traverso, an assistant professor in MIT's Department of Mechanical Engineering and a gastroenterologist at Brigham and Women's Hospital, treated a patient with celiac disease who had a reaction to a medication that contained inactive ingredients derived from wheat products.

Traverso and his team started by looking through the medical literature for reports of patients reacting to inactive ingredients.The researchers found some studies on patients who had allergic reactions to inactive ingredients such as lactose — present in about 45 percent of pills — as well as certain kinds of chemical dyes.

But they didn't find any studies looking at whether certain inactive ingredients may cause less extreme, but likely more common symptoms of food intolerance, such as bloating or stomach aches.

The researchers also dug into data about inactive ingredients themselves, using a database run by the National Library of Medicine. They found that active ingredients make up, on average, just over a quarter (29 percent) of the weight of an oral pill; the remaining 71 percent of the weight comes from inactive ingredients. On average, a pill contains more than eight different inactive ingredients but can contain up to 35, they reported.

But far than 35 inactive ingredients are available. In fact, drug companies have around 1,000 inactive ingredients to choose from when manufacturing pills, the researchers found. Of these ingredients, 38 of them, such as peanut oil, lactose and some dyes, are known allergens. But though most inactive ingredients are usually tested to see if they're toxic — and though they're found to not have a major effect on most of the population — these toxicology tests may miss certain small side effects in some people, according to the report.

The study found that 93 percent of pills contain at least one of the 38 allergens and that almost all of them contain substances that could be problematic for people with certain food intolerances, such as gluten or sugar.

Still, not all experts are convinced that inactive ingredients are particularly problematic.

Dr. John Kelso, an allergist and immunologist at Scripps Health in San Diego, California who wasn't involved in the study, doesn't see a cause for concern.

"Such reactions are quite rare," he said. "In most cases, the amount of the food protein [present] in the medication would not be sufficient to trigger an allergic reaction."

For example, the amount of egg protein that's present in flu shots is not enough to trigger reactions even in people with severe egg allergies allergic to eggs, Kelso told Live Science. Indeed, the the American Academy of Pediatrics revised recommendations for flu shots containing eggs, saying that it's no longer necessary to ask people if they are allergic to eggs before giving them the flu vaccine, because the risk is so minimal, he said.

As such, "for the vast majority of patients with [a] food allergy, there is no reason for them to avoid medications with [inactive ingredients] derived from the foods to which they are allergic," Kelso said.

He did note, however, one inactive ingredient in that may cause problems for people with allergies: gelatin. That's because some medications and vaccines are either administered intravenously or injected can contain larger amounts of gelatin, and can trigger allergy reactions. Therefore, these drugs should be avoided for people with gelatin allergies, but Kelso added that "even most of these patients tolerate [taking] gelatin in capsule form."

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Originally published on Live Science.

About how many people do you know who claim to have food allergies? While some of them might be legitimate, many purported food-allergy claims may be false alarms.

That’s according to new research that finds that 1 in 10 people in the U.S. are afflicted with food allergies, while nearly twice that number mistakenly believe themselves to be food-allergic.

Researchers surveyed more than 40,000 adults living across the country, finding that about 10 percent were allergic to one or more foods.

However, they also discovered that 19 percent of their subjects reported that they were allergic to certain foods, even though they didn't experience the physical reactions that typically accompany a genuine food allergy. [7 Strange Signs You're Having an Allergic Reaction]

While there's no question that food allergies are real — and for some, potentially life-threatening — people who self-diagnose as food allergic without consulting a medical professional may be misinterpreting their symptoms as an allergic reaction, the study authors wrote.

In those cases, what the individuals were experiencing could be a sign of food intolerance" or other food related conditions" rather than a true allergic response, lead study author Dr. Ruchi Gupta, a pediatrician and professor of pediatrics at Northwestern University Feinberg School of Medicine in Illinois, said in a statement.

Allergic reactions are the immune system's response to a trigger that is perceived as a threat. Regarding food allergies, when some people eat a certain type of food — such as nuts, shellfish, wheat or dairy — it broadcasts an alarm signal to their immune system, provoking reactions that can vary widely between individuals, according to the Centers for Disease Control and Prevention (CDC).

Symptoms of food allergies can include hives, itching and swelling in the nose and throat, and stomach pain or nausea. In extreme cases, food allergies may lead to anaphylaxis — a state of shock accompanied by low blood pressure and constricted airways — which can be fatal if untreated, according to the Mayo Clinic.

Shellfish is the most common food allergen in the U.S., affecting approximately 7 million adults, according to the study. Milk allergies affect nearly 5 million people, followed closely by peanut allergies, which affect about 5 million people. Other widespread allergens include tree nuts, fish, eggs, wheat, soy and sesame, the scientists reported.

Allergies can be inherited or acquired, sometimes unexpectedly — bites from a type of tick have been linked to the onset of an allergy to meat, and a woman who recently received a lung transplant also acquired her organ donor's peanut allergy.

In fact, developing food allergies in adulthood happens more frequently than expected, the scientists reported. They learned from the surveys that about 48 percent of the subjects who had food allergies first experienced at least one of them as an adult.

"We were surprised to find that adult-onset food allergies were so common," Gupta said.

If a person suspects that they have a food allergy, it is critical that they visit a doctor for testing and diagnosis before attempting to correct the problem by eliminating foods from their diet, Gupta said in the statement.

"If food allergy is confirmed, understanding the management is also critical, including recognizing symptoms of anaphylaxis and how and when to use epinephrine," he added.

The findings were published online today (Jan. 4) in the journal JAMA Network Open.

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Original article on Live Science.

Sometimes, you just really want a peanut butter and jelly sandwich. And, as long as you're not allergic to the ingredients, that's totally fine. At least, that's what one woman thought.

The 68-year-old woman, who had never had a peanut allergy, had a severe allergic reaction to the sandwich, according to a recent report of her case, which was published in August in the journal Transplantation Proceedings. But someone else did have a peanut allergy, it turned out: the donor who supplied the woman with a transplant lung.

It's a very rare occurrence for lung transplant recipients to acquire a food allergy from a donor organ, said lead case report author Dr. Mazen Odish, a fellow in pulmonary and critical care medicine at the University of California - San Diego Medical Center, who treated the woman. [27 Oddest Medical Cases]

There have only been about four or five case reports in which organ recipients have acquired peanut allergies with anaphylaxis following a lung transplant, Odish told Live Science.

Identifying the culprit

The woman in the case had needed a single-lung transplant to treat her emphysema, a condition in which the air sacs in the lungs become damaged, making it difficult to breathe. She received a new left lung from a 22-year-old male donor, Odish said.

The woman's recovery was going well after the transplant, but the day before she was scheduled to go home from the hospital, she felt tightness in her chest and found it very difficult to breathe, according to the report. Initially, her doctors weren't sure why she was experiencing these symptoms of respiratory failure, and tests done at the time didn't turn up any clear explanation for it.

It wasn't until the woman mentioned that her symptoms started immediately after she had eaten a PB & J sandwich that doctors began to suspect a food allergy, even though the woman lacked other common allergy symptoms, such as a rash or stomachache.

Because the woman had never had problems eating peanuts before, doctors contacted the transplant agency, who confirmed that the male donor had a known peanut allergy, according to the case report.

So, along with the lung, the woman also appears to have received a peanut allergy from the donor, Odish told Live Science.

Although it's rare for food allergies to be transferred from organ donors to transplant recipients, it does occur: cases of food allergies being acquired from organ donors have been reported after liver, kidney, lung, bone marrow, heart and kidney transplants, the authors wrote.

But not every transplant recipient who obtains an organ from a donor with food allergies picks up the sensitivity, which may turn up anywhere from days to months after the transplant. Studies have suggested, for example, that children and people who receive liver transplants may be more likely to develop food allergies from organ donors who have them.

Other research has shown that transplant-acquired food allergies occur more frequently when organ recipients are prescribed tacrolimus, an immunosuppressive drug used to reduce the risk of organ rejection following a transplant. The woman in this case had been on tacrolimus.

Skin tests later confirmed that the woman was allergic to peanuts, and she also tested positive for almonds, cashews, coconuts and hazelnuts. Doctors advised her to avoid peanuts and tree nuts, and she was given an EpiPen in case of another severe allergic reaction to these foods.

It's unclear if transplant-acquired food allergies remain a lifelong concern for patients, Odish said, because it's possible that the allergy may wane in some individuals. Allergy doctors will likely continue to test the woman for peanut and tree nut allergies to see if her tolerance to these foods change over time, he noted.

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Originally published on Live Science.

Scorching summer days can be tough without air conditioning, and you might find yourself searching for ways to stay cool, including using a fan at night. But is it healthy to sleep with a fan on?

Some recent headlines have made sleeping with a fan on sound downright dangerous. "Why Sleeping with Your Fan on Could Be Seriously Damaging Your Health," read one recent headline from the Mirror. "Sleeping with a Bedside Fan Could Pose Health Risks," read another, from LifeZette.

But experts say the reality is not that dire.

"There's nothing about a fan that's toxic," said Dr. Len Horovitz, a pulmonologist at Lenox Hill Hospital in New York City. "There's nothing wrong with circulating air." [7 Common Summer Health Concerns]

Indeed, sleep is very important, and you don't want to be sweating all night, Horovitz told Live Science.

But anything that causes rapid air movement, including a fan, can evaporate moisture from your mouth and nasal passages, drying them out, he said. Fans may also circulate dust, which could bother people, particularly if they have allergies.

If you do sleep with a fan on, Horovitz said it's a good idea to keep it at a safe distance from your bed and not have it blowing right on you. To guard against dust and other allergens, Horovitz recommended keeping an air filter in the bedroom. He also recommended performing daily sinus irrigation with saline, which can help with dry nasal passages, congestion and other nasal problems.

Cold air can also cause muscle contractions, and so exposure to this air at night may lead to a stiff neck in the morning. But Horovitz said this is more of a problem with air conditioning that's left on at night than it is with fans. If you do sleep with air conditioning on at night, Horovitz said the air shouldn't be blowing directly on you and the setting shouldn't be lower than 68 degrees Fahrenheit (20 degrees Celsius).

Original article on Live Science.

It all started when a woman's co-workers ramped up the air conditioning. For some reason, she broke out in hives. Concerned, the woman visited the doctor and got startling news: She was allergic to the cold.

The condition, known as cold urticaria (ur-tih-KAR-ee-uh), is rare, but it jibed with her past experiences, the woman's doctors wrote in a new Australian case report, published online April 3 in the journal Climacteric. The 40-year-old woman said she also got hives on windy days, while walking outside on cold mornings and after swimming in the ocean.

The latest episode was brought on because her co-workers, who were experiencing menopausal hot flashes, had cranked up the AC in the office, her doctors found. [7 Strange Signs You're Having an Allergic Reaction]

People with cold urticaria can also break out in hives if they come into contact with cold objects or consume cold foods or drinks, the doctors wrote. In fact, while examining the woman, the doctors pressed an ice cube against her arm for 10 minutes. After removing the ice, they saw a "well-defined wheal, consistent with the diagnosis of cold urticaria," the doctors wrote in the case report.

Despite her rare allergy, the doctors treated the woman as they would any patient with hives: They prescribed her antihistamines to relieve her symptoms. Here's why: When the immune system detects something potentially dangerous — in this case, the cold — certain white blood cells and tissue cells release histamines that find and attach to histamine receptors, Live Science previously reported. Once connected, these histamines induce an inflammatory response, such as increased blood flow, to help heal the site.

Antihistamines block these histamines, so the allergy can't lead to an inflammatory response, Live Science reported. However, in this case, the doctors also advised the woman to prepare for the cold — for instance, by taking antihistamines in advance if she knew she would be exposed to a chilly place.

They also recommended that she wear a long wet suit when swimming and that she swim with a partner, just in case her cold urticaria caused her to lose consciousness, they wrote in the case report. That's because swimming in very cold water can cause some people with cold urticaria to experience very low blood pressure, fainting or shock, according to the Mayo Clinic.

It's unclear what causes cold urticaria, but sometimes it's triggered by certain blood cancers and autoimmune diseases, said Dr. Tho Truong, an allergist at National Jewish Health in Denver who was not involved with the patient's care. In the woman's case, it's possible she inherited a trait that made her susceptible to the condition, as her mother has a similar, but milder, reaction to cold temperatures, the doctors wrote in the case report.

Up to 3 percent of the population experiences hives, and the percentage who have cold urticaria is even lower, Truong told Live Science. However, it's possible that even a person with run-of-the-mill hives will develop the red splotches after a temperature change, such as when getting into a hot shower or going into the icy outdoors.

"It's not like they're allergic to heat [or cold], but they have this underlying condition that makes their immune cells very sensitive to these physical changes," Truong said. "They don't necessarily have cold-induced urticaria; they just have urticaria," or hives.

An allergy to the cold may be rare, but it's not the only unusual allergy out there. For example, a toddler in Minnesota is allergic to water, a condition known as aquagenic urticaria, Live Science reported earlier this year. 

Original article on Live Science.

An "acupuncture" session using stings from living bees triggered a lethal allergic reaction in a 55-year-old woman at a clinic in Spain.

During the treatment, the woman was deliberately stung by live bees to treat her muscle contractions and stress, according to a recent case report. The blending of bees and acupuncture is a type of "apitherapy" — a term that describes an increasingly popular practice of treating various medical conditions with substances derived from honeybees.

However, there's scant clinical evidence that there are any benefits to these procedures, and in fact, they may be harmful. In this case, bee venom from the stings led to a severe allergic reaction that caused the woman's death, researchers explained in the report. [Spider Bites and Bee Stings: Symptoms and Treatments]

Following a sting administered at a private clinic, the woman began to wheeze and then lost consciousness. She was transported to a local hospital, where she was diagnosed with a massive stroke that resulted in a permanent coma; she died several weeks later from multiple organ failure, the researchers noted in their report, which was recently published in the Journal of Investigational Allergology and Clinical Immunology.

Therapies using bee venom date back thousands of years, and can be traced to ancient civilizations in China, Greece and Egypt, according to a July 2012 study. Today, apitherapy is most commonly practiced in Asia, South America and Eastern Europe, and is used to treat immune-related diseases, some types of cancer, and conditions that affect the musculoskeletal system, such as rheumatism and arthritis, researchers reported in a study published in May 2015 in the journal PLOS ONE.

But bee venom therapies are often linked to adverse reactions, and there is little published research to support their safety and effectiveness, according to the new case report.

For people who are sensitive to bee venom, the venom's compounds can trigger allergic reactions that range from mild to severe. In extreme cases, they cause anaphylaxis, an allergic reaction that can strike within moments after exposure to the allergen, and can be life-threatening. During anaphylaxis, the body floods with chemicals that induce a state of shock; blood pressure drops and the tongue and throat can swell, making it difficult to breathe, according to the Mayo Clinic.

The hormone epinephrine, also known as adrenaline, can ease anaphylaxis symptoms, but the apitherapy clinic in Spain did not have any on hand. And though the unconscious woman was given epinephrine once medical help arrived, the ambulance didn't show up until about 30 minutes after the clinic workers placed the call, according to the case report.

Curiously, this wasn't the woman's first visit to the apitherapy clinic; in fact, she had been visiting the clinic and receiving bee acupuncture every four weeks for the past two years, with no adverse effects reported.

What likely happened is that she developed a sensitivity to honeybee venom over the course of her treatment, "and the last sting was the clinically relevant one that was fatal," Dr. Andrew Murphy, an allergist with the Asthma Allergy and Sinus Center in Downingtown, Pennsylvania, told Live Science in an email. In other words, people can develop a sensitivity to allergens such as bee venom through regular exposure.

"What was even more galling and sad is that this clinic did not even have epinephrine available to treat the patient in case of a reaction," Murphy added.

The study authors suggested that more rigorous measures should be taken by apitherapy clinics to identify people's sensitivity to bee venom — particularly if they have been receiving stings over time — and that people should be informed of the inherent hazards in these largely untested procedures. In fact, those on the receiving end of a bee's stinger should probably consider avoiding bee acupuncture entirely, the physicians added.

"The risks of undergoing apitherapy may exceed the presumed benefits, leading us to conclude that this practice is both unsafe and unadvisable," the researchers wrote.

Original article on Live Science.

We can't live without water, but for one toddler in Minnesota, contact with plain old H2O can be dangerous — she has an extremely rare allergy that causes her to break out in hives and rashes anytime she touches water, according to news reports.

The 18-month-old, Ivy Angerman, was recently diagnosed with aquagenic urticaria, or an allergy to water, according to local news station Fox 9. Her doctors say she may be the youngest person ever diagnosed with the condition, which more often appears around the age of puberty.

Ivy's parents have taken cellphone videos to show their daughter's severe reactions during bath time. She can be in the water for only 15 seconds before her symptoms appear, Fox 9 reported.

"Is she ever going to be able to go to daycare? Is she ever going to be able to go to public school? Is she able to ever go in the ocean? I don't know," Ivy's mother, Brittany Angerman, told Fox 9 after her daughter's diagnosis. [9 Weirdest Allergies]

Aquagenic urticaria is so rare that fewer than 100 cases have ever been reported in the medical literature, according to a 2011 paper.

People with the condition rapidly develop hives after contact with water, regardless of its temperature, according to the National Institutes of Health's Genetic and Rare Diseases Information Center (GARD). The rash most commonly develops on the person's neck, upper trunk and arms, although it can appear anywhere on the body. The rash typically goes away within 30 to 60 minutes after the exposure, GARD says.

The exact cause of the condition remains a mystery. But researchers have several theories about how the condition develops.

One possibility is that the hives are not caused by water itself, but by another substance dissolved in the water (such as chlorine) that enters the skin and triggers an allergic reaction, according to GARD. Another theory is that, in people with the condition, a substance found on their skin produces a "toxic" material when it interacts with water, leading to hives, GARD says.

There's no cure for the condition, and doctors have limited data on which treatments work best for symptoms. But treatments can include antihistamines, exposure to ultraviolet B (UVB) light (called phototherapy) and creams that serve as a barrier between the water and the skin, GARD says.

Ivy's parents said that their daughter's symptoms have improved somewhat now that she is taking antihistamines.

Doctors have also recommended that Ivy bathe in purified water, and live in a home with central air conditioning so she doesn't overheat (as water in sweat can also trigger the condition). Ivy's parents are in the process of moving out of their home, which was built in 1901, Fox 9 reported.

Original article on Live Science.

Some people who experience seemingly mysterious allergic reactions may have a rare type of allergy to red meat, a new study finds.

The study evaluated 70 people who had "unexplained frequent anaphylaxis," which means they had life-threatening allergic reactions that didn't have an apparent trigger.

About 9 percent of these participants tested positive for an allergy to a molecule called galactose-alpha-1,3-galactose, or "alpha-gal," which is found in beef, pork, lamb and other red meats. When these patients cut red meat out of their diet, none of them experienced anaphylaxis during the 1.5-to-three-year follow-up period, the researchers said.

Diagnosing an alpha-gal allergy can be a challenge, in part because patients with the condition often experience a delayed allergic reaction that occurs about 3 to 6 hours after they consume red meat, the researchers said. In contrast, most allergic reactions to other foods occur about 5 to 30 minutes after a person consumes the food. [9 Weirdest Allergies]

"This unusually long time gap between a meal and an allergic reaction is probably a big reason that alpha-gal allergies are often initially misdiagnosed," Dr. Dean Metcalfe, chief of the Mast Cell Biology Section at the National Institute of Allergy and Infectious Diseases (NIAID) and co-author of the study, said in a statement. (Mast cells are a type of immune cell that plays a role in allergies.) "If you start to have trouble breathing in the middle of the night, you probably are not going to blame the hamburger you had for dinner," Metcalfe said.

What's more, most routine allergy tests do not check for alpha-gal allergies. The researchers said their new study "supports the need for routine screening for this sensitivity as a cause of anaphylaxis," they concluded.

Interestingly, people with alpha-gal allergies often have a history of tick bites from lone star ticks(Amblyomma americanum). Indeed, in the current study, all of the patients with alpha-gal allergies had experienced lone-star-tick bites. Earlier research suggested that these tick bites can play a role in causing this rare allergy.

"We often think of ticks as carriers of infectious diseases, such as Lyme disease, but the research strongly suggests that bites from this particular species of tick can lead to this unusual allergy," said study co-author Dr. Melody Carter, also of the Mast Cell Biology Section at NIAID. "The association is increasingly clear, but we still need to discover exactly how these two events are linked and why some people with similar exposure to tick bites seem to be more prone to developing alpha-gal allergy than others."

The new study was published online Nov. 21 in the journal Allergy.

Original article on Live Science.

A sting from a yellow jacket is typically a minor annoyance, but a wasp bite turned into a major medical problem for a 45-year-old British man: He had a severe allergic reaction to the bite and, as a result, suffered a heart attack, according to a recent report of the man's case.

The man was diagnosed with Kounis syndrome, or "allergic myocardial infarction," in which a severe allergic reaction is accompanied by symptoms of chest pain (known as angina) that may progress to a heart attack. 

Although Kounis syndrome is rare, there are medical case reports of the syndrome that have been linked to allergic reactions to foods, insect stings and certain drugs. [27 Oddest Medical Cases]

In this man's case, he was stung by a yellow jacket on his left arm as he got into his van. Minutes later, he began to feel dizzy and itchy all over, and a rash appeared on his body, according to the case report.

The man's left hand began to feel heavy and achy, and hours later, this pain became more frequent and spread to his left arm, shoulder and back. He called for an ambulance, and on the ride to the hospital, he suffered a heart attack, the case report said.

Paramedics were successful at resuscitating him, but doctors were initially unsure what caused this life-threatening emergency.

From allergy to emergency

The man had been stung by insects multiple times in the past, but he experienced no reaction to these bites, according to the case report's lead author, Dr. Benjamin Cross, who, at the time of the case, was a medical student at Blackpool Victoria Hospital in Blackpool, England.

The man has a genetic tendency to develop allergic diseases, including a medical history of asthma and eczema, Cross said. However, the man had never had a severe allergic reaction, Cross said. 

But there were some reasons to be concerned about the man's heart heath. The 45-year-old had been smoking a pack of cigarettes a day for more than 30 years, Cross told Live Science. (Smoking has been linked with an increased risk of heart disease.) Prior to this incident, the man had some buildup of plaque in his arteries, which also put his heart at risk, Cross said.

But why would an insect sting trigger a heart attack in a middle-age man?

The wasp bite most likely caused a type of white blood cell, known as mast cells, to react, which, in turn, caused the plaque in his artery to burst, Cross said. When plaques burst, it causes a clot, which blocks the artery and reduces blood flow. A loss of blood flow to an area of the heart causes heart cells to die, which results in a heart attack, Cross explained.

To repair the man's blocked artery, doctors inserted a stent. After he went home from the hospital, his allergist recommended that he receive allergy shots containing small doses of the wasp venom that initially triggered his severe allergic reaction, Cross said. This treatment will sensitize his immune system and reduce the chance that another yellow-jacket sting will cause an allergic reaction, he added.

But as a precaution, the man was advised to carry an EpiPen, which can deliver a quick dose of the hormone epinephrine, to help prevent another severe allergic reaction, Cross said.

The case report was published online Sept. 7 in the journal BMJ Case Reports.

Original article on Live Science.

When a person has a severe allergic reaction, an injection of epinephrine can be lifesaving, and the sooner, the better.

But a new study finds that less than 40 percent of kids who had this type of allergic reaction, called anaphylaxis, received an injection of epinephrine before they got to the emergency room or an urgent care clinic.

Epinephrine can be given immediately to a child with anaphylaxis using an epinephrine auto-injector, a device that automatically injects a dose of the drug into a person's body. EpiPens are one type of epinephrine auto-injector. [8 Strange Signs You're Having an Allergic Reaction]

In the study, the researchers looked at medical records from more than 400 kids and teens who went to either the emergency room or the urgent care clinic at Nationwide Children's Hospital in Ohio for a severe allergic reaction. Nearly half of the patients were ages 5 or younger.

Only 36 percent of the kids in the study received epinephrine before arriving at the hospital or clinic, the researchers found. Not every patient included in the study ended up being treated with epinephrine once they arrived, the researchers noted. But 50 percent of the patients in the study did receive it when they arrived at the hospital or clinic, including some who had already gotten it before seeking care, the researchers found.

The children and teens were more likely to have received the drug prior to arriving at the hospital if their allergic reaction struck while they were at school, the researchers found.

"Treatment with epinephrine is often delayed or avoided by parents and caregivers," lead study author Dr. Melissa Robinson, an allergist at the National Jewish Hospital in Denver, said in a statement. "And sometimes, antihistamines are used even though they are not an appropriate treatment." Antihistamines are another common type of allergy medicine.

A majority of the kids and teens included in the study had had an anaphylactic reaction in the past, the researchers noted, but less than half of those patients had been prescribed an epinephrine auto-injector. And among those who did have a prescription, only about two-thirds had the device with them at the time of allergic reaction.

But the symptoms of anaphylaxis "occur suddenly and can progress quickly," senior study author Dr. David Stukus, an allergist at Nationwide Children's Hospital, said in a statement. "It's vital to keep your epinephrine with you if you suffer from any sort of severe allergy."

In fact, people with such allergies should also carry a second dose of the medicine, Stukus said. "When in doubt, administer [that second dose], too." 

The study was published July 12 in the journal Annals of Allergy, Asthma and Immunology. 

Originally published on Live Science.

When it comes to giving allergy medicine to kids, many parents are doing things that could potentially cause problems, a new poll finds.

Parents who were polled said they had trouble figuring out the right dose of allergy medications to give to their children, and some said they used adult versions of the drugs instead of child versions, according to a new poll.

When using adult allergy medications, "parents should be very careful to give their child the correct dose," Dr. Gary Freed, a pediatrician at the C.S. Mott Children's Hospital in Michigan and co-director of the poll, said in a statement. "Doses greater than recommended for children can result in more severe side effects,” Freed said. (Some side effects of allergy medications for kids are excessive drowsiness and headaches, according to the Food and Drug Administration.)

For the poll, researchers at Mott surveyed a nationally representative sample of U.S. adults who had children ages 6 to 12.

Overall, more than half the parents (55 percent) said they had given allergy medicine to their child in the past year. About 1 in 5 parents (21 percent) reported that it was hard to figure out the right dose of allergy medications for their child.

What's more, 15 percent of parents gave their child an adult form of the allergy medicine. Of these, about one-third gave their child the dose recommended for adults, while two-thirds used a partial adult dose. [How to Cope with Allergies & Asthma in 2017]

Although adult allergy medicines often contain the same ingredients as those for kids, the labels on the adult versions often don't include instructions on how much of the medicine to give children, according to Mott.

The poll also found that 18 percent of parents did not check the expiration date on the allergy medicines before giving them to their children. Although expired medicines are unlikely to be dangerous, they could lose their potency over time, Freed said.

If parents aren't sure which allergy medication is right for their child, or how much to give their child, they should check with their health care provider before using the medicines, Freed said.

Freed advises parents to read medication ingredients to help them choose the right option for their child. It's a good idea to "match" a child's symptoms to the ingredients in the product — for example, antihistamines can help with symptoms such as a runny nose and itchy eyes, while decongestants can help with a stuffy nose, according to Mott.

The poll is based on a survey of 1,066 adults, and was administered in January 2017.

Original article on Live Science.

People who are allergic to one type of tree nut, such as cashews, may not be allergic to all other kinds of tree nuts, though they are often told to avoid those nuts, a new study finds.

The study's authors suggest that people who have developed allergic symptoms in the past to one tree nut, and who have been avoiding eating all other tree nuts based on medical advice may wish to undergo a properly supervised "oral food challenge" test, to see if they are truly allergic to other tree nuts. However, more research is needed to confirm the new findings.

Tree nuts are a group of eight nuts: almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pistachios and walnuts. Researchers in the new study found that 76 percent of the participants who had an allergy to one type of tree nut could pass an oral food challenge test with a different tree nut. This test involves eating very small amounts of a food under medical supervision to see if the individual develops any symptoms of an allergic reaction, such as wheezing, a rash, an upset stomach or facial swelling. [How to Cope with Allergies & Asthma in 2017]

An oral food challenge is a closely supervised medical procedure, and people with known allergies to tree nuts or peanuts should not be experimenting with eating nuts on their own, because this could trigger a severe allergic reaction known as anaphylaxis.

Passing an oral food challenge test is considered the most accurate way for people to demonstrate that they do not have a food allergy, according to a statement from the American College of Allergy, Asthma and Immunology, an association of allergy specialists that publishes the medical journal in which the new study appears.

"We found that patients with tree nut allergies can be allergic to one nut but be tolerant to another tree nut," said Dr. Christopher Couch, an allergist at the Allergy Asthma Clinic, Ltd. in Phoenix, and the lead author of the study published today (March 27) in the journal Annals of Allergy, Asthma and Immunology.

Allergies vs. sensitivities

Two other tests, a blood test and a skin-prick test, are also used to diagnose food allergies. However, a positive result on either of those tests does not always indicate that a person is truly allergic to the food being tested, Couch told Live Science. A food challenge is the next step to confirm the allergy, he said.

About 1 percent of children in the United States are allergic to tree nuts, according to an estimate published in the journal Pediatrics in 2011.

In the new study, researchers analyzed data from the medical records of 109 patients who had visited allergy clinics affiliated with the University of Michigan Medical Centerduring an eight-year period, from 2007 to 2015. Most of the patients were children.

The study included only people with known allergies or sensitivities to a single tree nut. These participants were given an oral food challenge test at a clinic, to find out whether they were also allergic to other nuts. [8 Strange Signs You're Having an Allergic Reaction]

In the research, people who had developed allergy symptoms after eating a specific tree nut were considered to be allergic to that nut, while people who had positive blood or skin-prick test results to tree nuts but had never actually eaten that food were considered sensitized, Couch explained.

High pass rates

The study found that 76 percent of people with allergies to a specific nut passed the oral food challenge test for a different type of tree nut. In addition, 91 percent of the participants passed the food challenge if they had food sensitivities to a tree nut rather than true allergies.

Interestingly, all of the participants who ate an almond during the food challenge passed the test, whereas the passage rates for people given a walnut or a cashew were lower, at 82 percent and 79 percent, respectively.

It was surprising to find that everybody passed the almond food challenge but not those of other tree nuts, Couch said. The reasons why are not exactly clear, but it's possible that something about the structure of the almond is unique, he said. [9 Myths About Seasonal Allergies]

The researchers also looked at people with peanut allergies, who had positive blood or skin-prick tests for tree nuts but had never eaten any of these nuts. (Peanuts are not tree nuts, but allergy specialists usually tell people with peanut allergies to avoid tree nuts, too.)

Results showed that 96 percent of the people with peanut allergies passed the oral food challenge with tree nuts, meaning that only 4 percent developed an allergic reaction when given a small amount of an individual tree nut.

One of the limitations of the study is that the patients were drawn from only one health care system in Michigan, and so may not be representative of people throughout the United States, the authors noted. 

Originally published on Live Science.

In 2017, Live Science is bringing our readers a monthly series on personal health goals, with tips and tricks we've gathered from the many health experts we've interviewed. Each month, we'll focus on a different goal, and the goal for April is coping with allergies. Follow us on Facebook and Twitter to connect with other readers who are working toward these goals.

Jump to: January — Lose Weight | February — Eat Healthy | March — Start Exercising | April — Cope with Allergies | May — Protect Yourself from Sun and Heat

Soon, the days will be getting warmer, shoots of green grass will appear and trees will be bursting with colorful blossoms. But for some people, the arrival of spring also brings symptoms of seasonal allergies — sneezing, wheezing, watery eyes and a running nose — which can make this a miserable time of year. However, there are several steps you can take to get your allergies under control in 2017.

Here's your guide to coping with with allergies and asthma this year.

Allergies: The basics

An allergy is a reaction of your immune system to what are usually harmless, run-of-the-mill substances, such as pollen, cat hair or peanuts. When you're exposed to your allergy trigger (called an allergen), your immune system produces proteins called immunoglobulin E (IgE) antibodies. These antibodies then put out signals that cause the release of other chemicals, such as histamine, which in turn cause your allergy symptoms.

According to the American College of Allergy, Asthma and Immunology (ACAAI), more than 50 million people in the U.S. experience allergies each year.

Allergies are also often tied to asthma, a condition in which people's airways become inflamed and narrowed, which can lead to coughing, chest tightness, wheezing and difficulty breathing. In some people, the same substances that trigger allergies can also trigger symptoms of asthma, according to the Mayo Clinic.

Read up on some allergy basics below:

• The 5 Most Common Allergies
• Sniffle Detective: 5 Ways to Tell Colds from Allergies
• 7 Allergy Myths (and the Truth Behind Them)
• Got Allergies? Blame Neanderthals
• 8 Strange Signs You're Having an Allergic Reaction
• Can You Outgrow Your Allergies?

All about allergy season

There is no single "allergy season." People's allergy symptoms may vary throughout the year, depending on where they live and the types of substances they're allergic to. And some people may have symptoms year round.

Still, many people experience a worsening of their allergies around springtime, when more plants produce pollen. This includes people with allergic rhinitis, or hay fever. Springtime allergies can start as early as February and last until summer, according to the ACAAI. And people who are allergic to ragweed often experience symptoms in the fall, as this plant blooms from August to November, the ACAAI said. People who are allergic to dust mites, pet hair or mold may have symptoms at any time of year.

Here's a look at how the seasons, and the weather, can affect your allergies.

• Why Do People Get Sick When the Seasons Change?
• Why Do Allergies Get Worse in Autumn?
• 7 Strategies for Outdoor Lovers with Seasonal Allergies
• 'Pollen Vortex'? Long Winter Worsens Allergies in Spring
• Climate Change May Worsen Mold Allergies
• What Is 'Thunderstorm Asthma'?

The lowdown on allergy testing

Before you can tackle treating your allergies, it helps to first know what you're allergic to. That's where allergy testing comes in. There are several types of allergy tests, including skin tests, food "challenge" tests and blood tests.

More information on allergy testing:

• Many Parents Who Think They Have Food Allergies Actually Don't
• Children with Asthma May Have Peanut Allergies
• Why Adults Diagnosed with Asthma May Not Actually Have It

Reduce exposure to allergy triggers

Once you know what you're allergic to, you can take steps to reduce exposure to your allergy triggers.

For instance, if you're allergic to pollen, you might try to stay inside on dry and windy days, the Mayo Clinic said. On days when pollen counts are high, you should avoid outdoor activity, particularly in the mornings, when pollen counts are highest, the Mayo Clinic said.

You can also consider using a portable high-efficiency particulate air (HEPA) filter in your home to reduce indoor levels of pollen, pet hair, dust and other substances that you may be allergic to, the Mayo Clinic said.

More information on reducing allergy triggers:

• Tips to Nip Allergies in the Bud
• Allergy Relief Really Is Possible
• Oral Allergy Syndrome: 6 Ways to Avoid an Itchy, Tingling Mouth

Finding the right allergy meds for you

To reduce symptoms of allergies, you can choose from a number of treatments, including pills, nasal sprays, eye drops and allergy shots. The kind of medication you take will depend on your symptoms and the severity of your allergies. You can consult with your doctor about which medication is right for you. Below, we've summarized the various types of allergy medications and the symptoms they treat.

More information on allergy medications:

• Allergy Medications: Which Drugs Treat Which Symptoms
• Most Allergy Sufferers Not Getting Relief from Over-the-Counter Meds
• Allergy Meds Can Pose Driving Hazard, FDA Says
• Why Do Antihistamines Make You Drowsy?

Original article on Live Science.

Parents who are wondering when exactly they should start feeding peanut-containing foods to their infants to reduce the children's risk of peanut allergies can now turn to new guidelines.

The guidelines, which are sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), outline when and how parents should introduce peanut-containing foods to their children, depending on the child's risk of developing a peanut allergy.

"We expect that widespread implementation of these guidelines by health care providers will prevent the development of peanut allergy in many susceptible children and ultimately reduce the prevalence of peanut allergy in the United States," Dr. Anthony Fauci, director of NIAID, said in a statement.

The guidelines are based on recent studies that have found that feeding children peanut-containing foods early in life actually reduces the kids' risk of developing allergies to this food.

For the guidelines, infants are divided into three groups: those at high, moderate and low risk for developing a peanut allergy. The recommendations for these groups are as follows:

High-risk infants: These infants already have severe eczema, a severe egg allergy or both, putting them at high risk for developing a peanut allergy. Infants in this group should be fed peanut-containing foods as early as 4 to 6 months, if they have already started eating solid foods, the guidelines state. However, parents whose children fall into this group should first check with their doctors before starting their infants on peanut-containing foods.

A doctor may recommend that the infant undergo an allergy test, or have peanut-containing foods fed to him or her for the first time at a doctor's office, to determine whether it's safe for the infant to start eating peanut. If it seems likely that the child is already allergic to peanuts, because of a very large reaction to a skin test for peanut allergies, then the doctor may suggest that the child avoid peanuts altogether, said allergist Dr. Matthew Greenhawt, chair of the American College of Allergy, Asthma and Immunology's Food Allergy Committee, who was a co-author of the guidelines. [The 5 Most Common Allergies]

Moderate-risk infants: These infants have mild to moderate eczema. For these children, parents should introduce peanut-containing foods around 6 months of age, and parents do not need to seek evaluation from a doctor beforehand, the guidelines said. But parents can always consult with their doctors if they have questions.

Low-risk infants: These infants do not have eczema or an egg allergy. They can have peanut-containing foods freely introduced into their diets along with other solid foods, the guidelines said.

In the past, doctors recommended that children who were at high risk for food allergies should avoid potentially risky foods, such as eggs and peanuts, until they were 2 to 3 years old. But in recent years,  experts have changed their views on this issue. One particularly influential study found that, among children at high risk for developing a peanut allergy, those who were fed peanut-containing food early in life were about 80 percent less likely to develop a peanut allergy, compared to those who avoided the food.

The new guidelines are the first to formally recommend early peanut introduction for kids with a high risk of developing allergies to peanuts.

It's important to note that whole peanuts pose a choking risk to young children, and so parents should not feed whole peanuts to infants. Instead, parents could use age-appropriate foods, such as smooth peanut butter, the guidelines said.

The guidelines were published today (Jan. 5) in the Journal of Allergy and Clinical Immunology.

Original article on Live Science.

Hundreds of people in Melbourne, Australia, experienced breathing problems during a recent storm, in what's being called an outbreak of "thunderstorm asthma." But what's behind this rare phenomenon?

On Monday (Nov. 21) evening, the ambulance service in Melbourne, called Ambulance Victoria, received more than 1,800 calls during the storm, which is about six times more than usual, according to the BBC.

About 200 calls were for cases of asthma, and 600 calls were for people with breathing difficulties, Mick Stephenson, executive director of emergency operations at Ambulance Victoria, told the BBC. "A lot of people who called last night had never had asthma before," Stephenson was quoted as saying. There were also two deaths from asthma during the storm. [9 Myths About Seasonal Allergies]

Similar events have been reported in England, Canada, Italy and the United States. For example, during a heavy thunderstorm in 1994 in London, 640 patients with asthma or breathing difficulties visited the emergency room — a number 10 times higher than the expected number of asthma patients on a given day, according to a 2012 review. About 280 of those patients had never had asthma before.

Many people who experience "thunderstorm asthma" have a common condition known as hay fever, in which they are allergic to pollen or other substances in the air, according to the Australasian Society of Clinical Immunology and Allergy (ASCIA).

It's thought that these outbreaks occur because, during thunderstorms, pollen grains rapidly absorb water and rupture, leading to the release of hundreds of small particles into the air, ASCIA says. These particles can penetrate deep into people's lungs and trigger asthma attacks, ASCIA says. Some outbreaks of thunderstorm asthma have also been linked with increased levels of fungal spores in the air.

It's also thought that gusty winds in thunderstorms help to spread pollen particles and other allergy-inducing substances. A 2008 study that looked at emergency room visits in Atlanta over a 10-year period found that there were 3 percent more visits for asthma on days following thunderstorms. The link between asthma visits and thunderstorms was strongest when the wind gusts during the storm were intermediate to high, the study found.

It's suspected that the outbreak in Melbourne was caused by high levels of ryegrass pollen, the BBC said. On Monday, the level of rye-pollen particles in the air was more than double the level that's typically considered high, the BBC said.

People with asthma triggered by pollen can take asthma medications to prevent or treat their symptoms, ASCIA says.

Original article on Live Science.