What Is Chickenpox? Causes, Symptoms & Treatment
A child with chickenpox lesions.
Credit: Shutterstock

Chickenpox is a contagious disease characterized by many itchy, red bumps all over the body. Children younger than age 15 are most likely to get it, but older children and adults can become infected as well. Chickenpox (sometimes spelled chicken pox) is highly contagious and can be spread by contact with the affected areas, or by an infected person sneezing or coughing on an uninfected, unvaccinated person.

Before the chickenpox vaccine was introduced in the United States in 1995, about 4 million people got the disease every year, according to the Centers for Disease Control and Prevention (CDC). But the availability of the vaccine lead to a dramatic drop in cases: between 2000 and 2010, chickenpox cases declined by nearly 80 percent, the CDC said.

Chickenpox, or varicella, is caused by the varicella-zoster virus, which is related to the herpes virus. The infection has three stages. It starts out with the appearance of little, itchy bumps. Those bumps turn into blisters filled with fluid. The final stage is the scabbing over of the bumps.

Since new bumps can appear over several days, it's possible to have all three stages of the rash at the same time, according to the Mayo Clinic.

In addition to the rash, chickenpox can cause fever, headache, dry cough or loss of appetite.

The illness usually lasts about 5 to 10 days. People with chickenpox are contagious starting about a day or two before their symptoms appear, and up until all of their blisters have turned to scabs, according to the CDC.

Children usually recover from chickenpox without any major issues. However, the illness can cause more severe symptoms for pregnant women, newborns whose mothers weren't vaccinated or haven't had the virus before, teens, adults, people with impaired immune systems and people taking certain medications.

Chickenpox "can cause hospitalization and, in rare cases, death," said Dr. Jason S. Applebaum, a dermatologist and fellow of the American Academy of Dermatology. "Fortunately, since the beginning of administration of the vaccine in 1995, hospitalizations have declined by nearly 90 percent, and there have been [only] a small number of fatal cases of chickenpox."

According to the CDC, complications of chickenpox include the following:

  • Dehydration.
  • Pneumonia.
  • Blood infections (sepsis).
  • Bacterial infections of the skin and soft tissues, including infections with Group A streptococcus bacteria.
  • Bleeding problems.
  • Infection or inflammation of the brain (encephalitis or cerebellar ataxia).

Chickenpox is typically diagnosed just by the visible symptoms. A doctor will also check for a fever of between 101 and 102 degrees Fahrenheit (38.3 to 38.9 degrees Celsius) and a headache.

However, a blood test or analysis of a blister sample may also be performed to confirm the diagnosis. Doctors may also conduct tests in people at high risk for catching chickenpox, including pregnant mothers, newborns, people who are about to undergo organ transplants and people with HIV or AIDS, in order to check whether or not they are immune to chickenpox, according to the American Association for Clinical Chemistry.

Healthy children typically do not require any specific medical treatment for chickenpox, according to the Mayo Clinic. But doctors may prescribe antihistamines to help stop the itching.

However, if the patient falls into a high-risk group, a doctor may prescribe an antiviral like acyclovir (under brand name Zovirax) or immune globulin intravenous, known as IGIV, to take within 24 hours of the appearance of chickenpox symptoms, according to the Mayo Clinic. For adults, valacyclovir (brand name Valtrex) or famciclovir (known as Famvir) may be prescribed.

Aspirin should never be given to anyone with chickenpox because the medication has been linked to a potentially fatal condition called Reye's syndrome, which causes organ damage, according to the National Institutes of Health. Taking acetaminophen (Tylenol) or ibuprofen (Advil or Motrin) can help relieve the fever associated with chickenpox.

There are several home remedies that may also help, such as:

  • Cool baths.
  • Applying calamine lotion.
  • Getting lots of rest.
  • Eating foods that don't irritate chickenpox sores that may be in or around the mouth.
  • Wearing gloves to prevent scratching that can lead to scarring.

Perhaps the best way to "treat" chickenpox is to never get it at all. The CDC recommends two doses of the chickenpox vaccine. Children should receive the first dose at ages 12 to 15 months, and again at ages 4 to 6. Two doses of the vaccine are about 90 percent effective at preventing chickenpox, according to the CDC. For the small percentage of people who catch chickenpox even after vaccination, the disease is usually milder with fewer blisters and little to no fever.

Teens and adults who have not been vaccinated and have never had chickenpox should get two doses of the vaccine, 28 days apart, the CDC says.

People who should not receive the vaccine, according to the CDC, include:

  • Pregnant women, who should wait until after giving birth to get the vaccine.
  • People who currently have a serious illness.
  • people who have been allergic to the vaccine.
  • People allergic to gelatin or neomycin (components of the vaccine).
  • People who may have had a blood transfusion in the last five months.

People with weakened immune systems, such as those with HIV or cancer, should speak with their doctor about whether they should get the chickenpox vaccine.

Instead of getting the vaccine, some parents opt to expose their children to the virus by having them interact with a sick child. These are commonly called "chickenpox parties." But because chickenpox can cause serious complications, especially for infants, the CDC does not recommend that parents risk exposing their children to chickenpox at such parties.  

Dr. Cristie Columbus, an infectious disease specialist and associate dean for the Texas A&M College of Medicine, agreed that, though rare, complications from natural chickenpox disease do occur, so vaccination is a much safer option than naturally exposing a child to the disease.

Additional resources:

This article was updated on Nov. 16, 2018 by Live Science Senior Writer, Rachael Rettner. This article is for informational purposes only, and is not meant to offer medical advice.