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Allergy vs cold: which is it?

woman laying on a sofa blowing her nose
(Image credit: Getty Images)

There can be a lot of confusion between an allergy vs a cold, as the symptoms are similar. So which are you suffering with? 

According to Dr Tariq Mahmood, medical director at Concepto Diagnostics (opens in new tab), what exactly causes an allergy is unclear, but an allergic reaction is when your immune system defends itself against a substance that it perceives as a threat. 

“When you interact with a substance that you have an allergy to, your body reacts by releasing the hormone histamine to the affected area,” he explains. “A cold, on the other hand, is a virus that infects your nose and throat by invading the healthy cells. Your body responds by releasing chemicals that trigger virus-fighting cells. In a nutshell, an allergy is a reaction to a foreign substance; a cold is a respiratory infection caused by a virus.” 

When it comes to clearing congestion or treating hay fever and seasonal allergies, you may also ask yourself: what are the best air purifiers for allergies? Or do dehumidifiers help with allergies? There are a few ways to treat both conditions, and in this article we’ll go into more depth about an allergy vs cold, explaining the causes, symptoms, differences and treatments.

What are allergies and colds?

More than 50 million people in the US experience various types of allergies each year and they are the sixth leading cause of chronic illness in the country, according to the Asthma and Allergy Foundation Of America (opens in new tab). Meanwhile, every year American adults have on average two to three colds, according to the Centers for Disease Control and Prevention (opens in new tab).

So what exactly are colds and allergies? “A cold is a viral infection in your upper respiratory tract – your nose, throat, sinuses,” says Dr Luke Pratsides, from online health clinic Numan (opens in new tab).

“Symptoms include a runny nose, sore throat, headache, cough and temperature. You catch a cold when you inhale infected particles through your airways. These particles are spread through airborne droplets that have come from an infected person coughing, sneezing, or breathing. 

“The virus is also spread through contact with infected surfaces. If you touch a contaminated surface and then rub your eyes or touch your mouth, you could then become infected by the virus. Symptoms begin a few days after infection and will usually last a few days. People with weaker immune systems are more vulnerable to infection.

9 allergy season symptoms: Image shows woman in field

(Image credit: Getty)

On the other hand, he explains that an allergy, such as hay fever, is the body’s intolerant reaction to a particular substance. Your body is recognizing the substance as an ‘invader’ and triggers an immune response. 

“Allergies are common and can develop and subside,” he says. “Symptoms include sneezing, a blocked nose, itchy eyes, coughing, and a rash. Although you might experience similar symptoms when you have a cold or allergic reaction, the two are different. A cold is a viral infection that’s passed on from person to person, whereas an allergic reaction is caused by the body triggering an immune response to a particular substance. Unlike a cold, an allergic reaction is not infectious.” 

If you're concerned about signs of poor air quality in general, we've rounded up the best air purifiers for our favorite all-rounders for clean indoor air. 

Allergy vs cold: differences

Pratsides says the main differences between a cold and allergic reaction include: 

Causes

A cold is caused by an infection from a virus that enters through the airways. An allergy is the body’s reaction to a substance and is stimulated by the presence of the substance. Depending on the allergy, you might consume or breathe in the substance that you’re allergic to. This then triggers an immune response in the body. 

Infectiousness

A cold is infectious, meaning it can be passed from person to person. An allergic reaction cannot be caught from another person.

Time taken for symptoms to begin

From exposure to a virus, it usually takes a couple of days for symptoms of a cold to begin. But after exposure to a substance that you’re intolerant to, symptoms will appear much quicker, within seconds or minutes.

Symptoms

Although colds and allergic reactions share some similar symptoms (such as runny or blocked nose, watery eyes, sneezing, and coughing) there are also dissimilar symptoms. A fever is a symptom of a cold that isn’t triggered by an allergic reaction. When you have a cold, you might also experience aches and muscle pains. This doesn’t occur when you’re having an allergic reaction.

Mahmood adds: “A usual cold lasts between seven and 10 days for most people, while allergies can vary between temporary and lifelong. A specific allergic reaction can take between a few hours and a few days to fully end. 

“If you’re repeatedly exposed to an allergen – such as people suffering with constant hay fever symptoms during the summer due to increased pollen in the air – then it might feel like you’re experiencing a long-lasting reaction when it’s just repeated reactions as and when you get exposed.

“There’s no specific time of year when you’re more likely to catch a cold, but exposing yourself to large groups of people – like traveling by air or going back to school after the holidays – could make you more susceptible to catching a cold. As for allergies, it depends on the allergy and if you’re able to limit your exposure to the substance.”

Treating a common cold

Pratsides says that to treat a cold you should get plenty of rest and drink lots of fluids to stay hydrated. Having one of the best water bottles to hand can help you to keep on top of your liquid intake.

“To soothe a sore throat, gargle salt water,” he adds. “Recommended medications include paracetamol, ibuprofen and decongestants. But be aware that you can pass on your cold to those around you, so wash your hands regularly, avoid close contact or sharing things with others, like towels or the same glass for drinking.” 

Treating an allergy

“If you think you’ve had an allergic reaction but you’re not sure, visit your family doctor for a diagnosis and advice on treatment,” says Pratsides. “If you have a known allergy, try to avoid it where possible. If it can’t be avoided, treatments include antihistamines, decongestants, and steroid medicines. If you experience shortness of breath or swelling of your lips, tongue or throat, seek immediate medical advice.” 

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

Maddy is a freelance journalist and Level 3 personal trainer specializing in fitness, health and wellbeing content. She has been a writer and editor for 22 years, and has worked for some of the UK's bestselling newspapers and women’s magazines, including Marie Claire, The Sunday Times and Women's Health. Maddy loves HIIT training and can often be found working out while her two young daughters do matching burpees or star jumps. As a massive foodie, she loves cooking and trying out new healthy recipes (especially ones with hidden vegetables so the kids eat them).