Chickenpox is a common and highly contagious illness caused by the varicella-zoster virus. It spreads easily through contact with someone who has the virus. Most people who get chickenpox develop an itchy rash with blisters, along with symptoms such as fever and tiredness.

While the illness is usually mild in healthy children, it can cause serious problems in babies, teens, adults, pregnant women, and people with weakened immune systems. Since the introduction of the chickenpox vaccine, severe cases have become less common. With vaccination and supportive care, most people recover fully from chickenpox.

Chickenpox is a viral infection that causes illness and a generalized rash of itchy spots or blisters. Anyone can get chickenpox, but it is most common in children under 10.

Chickenpox is caused by the varicella-zoster virus, which is a member of the herpesvirus family. Most people who get chickenpox once are protected for life against infection, but it is possible, though uncommon, to get it more than once. People who have been vaccinated against chickenpox can still get the illness, although their symptoms are usually much milder and they recover more quickly.

Chickenpox usually causes mild symptoms that last four to seven days in most healthy children, leading them to miss several days of school or childcare. Babies, adults, and people who have certain risk factors can experience more severe symptoms and complications from the infection.

After a person recovers from chickenpox, the virus remains in the body but does not cause symptoms. However, it can reactivate later in life and cause shingles, which is a different condition that causes a painful rash and other symptoms.

Before the chickenpox vaccine became available in 1995, almost all children in the United States got chickenpox by age 10. Since the vaccine became available, the number of chickenpox cases has dropped sharply, and severe illness is now extremely rare.

Chickenpox spreads easily between people, either through the air or by contact with fluid from the blisters.

The varicella-zoster virus, which causes chickenpox, is highly contagious and can infect up to 90% of people who are not immune and are in close contact with someone with the disease. The virus can spread by breathing in particles released when an infected person coughs or sneezes, or by touching the fluid from blisters. It usually takes 10 to 21 days after exposure for symptoms to appear.

People who have been vaccinated can still get chickenpox, called breakthrough chickenpox, which is usually much milder. Vaccinated people with breakthrough chickenpox can also spread the virus to others, but they are usually less contagious if their symptoms are mild.

A person with chickenpox is contagious one to two days before the rash appears and stays contagious until all blisters have formed scabs or until no new spots have appeared for at least 24 hours. Chickenpox can also spread from people with shingles, which occurs when the same virus reactivates later in life. Someone who has never had chickenpox or who has not been vaccinated can get chickenpox by coming into direct contact with the fluid from shingles blisters or by breathing in virus particles from shingles blisters.

Risk factors for chickenpox center on not having immunity to the virus, close contact with infected people, and certain health conditions or life stages.

People at higher risk of getting chickenpox or having severe illness include:

• People who have not had chickenpox or the chickenpox vaccine, which means the body has no protection against the virus
• Babies, who have immature immune systems and can get sicker from the infection
• Adolescents and adults, who tend to have more severe symptoms than young children
• Pregnant women, who are at higher risk for serious illness and complications
• People with weakened immune systems, such as those with HIV/AIDS or cancer, or those taking medicines that lower the immune response
• People receiving steroid therapy, which can weaken the immune system
• People with chronic skin or lung diseases, who may have more severe symptoms
• Health care workers, teachers, childcare workers, and others who are in close contact with children or groups, which increases the chance of exposure
• Residents and staff in nursing homes or other group living settings, where the virus can spread quickly

Chickenpox is more common in places where people come into close contact with each other for prolonged periods, such as schools and childcare centers. Outbreaks are more likely to happen in these settings if people are not vaccinated.

Symptoms of chickenpox range from mild illness in healthy children to more severe disease in adults, babies, pregnant women, and people with weakened immune systems.

The most common symptom is a rash that turns into itchy spots and fluid-filled blisters that then scab. The rash usually starts on the chest, back, and face, then spreads to the rest of the body, including inside the mouth, eyelids, or genital area. A person may have hundreds of blisters, and the rash can be very uncomfortable.

Other symptoms that may appear one to two days before the rash include:

• Fever, a sign the body is fighting infection
• Tiredness, feeling sleepier or weaker than usual
• Loss of appetite, not wanting to eat as much as normal
• Headache, pain or pressure in the head

The rash and other symptoms usually last about four to seven days. In healthy children, the illness is often mild, with a fever of up to 102°F (38.9°C) and mild discomfort for 2 to 3 days. In adults, the fever may last longer, and the rash may be more widespread.

Some people who have been vaccinated still get chickenpox, but their symptoms are usually milder. They may have few or no blisters, just red spots, and little or no fever.

To diagnose chickenpox, a doctor typically reviews medical history, performs a physical exam, and may order one or more diagnostic tests.

Doctors usually recognize chickenpox by its classic rash and symptoms. In most cases, no special tests are needed. However, if the diagnosis is unclear or if there are concerns about complications, a doctor may order tests such as:

• Polymerase chain reaction (PCR) test, which looks for the virus’s genetic material in fluid from a blister or scab
• Blood tests, which can show if the body is fighting a new infection or has immunity from a past infection or vaccination

Lab tests are especially helpful for confirming chickenpox in people who have been vaccinated, since their symptoms may be mild and look like other illnesses. Testing can also help doctors decide on the best treatment, especially for people at higher risk of complications. In addition, testing lets high-risk people know if they have come into contact with the virus, so they can seek preventive treatment, if appropriate.

Treatment for chickenpox aims to relieve symptoms and prevent complications, with antiviral medications given to those at increased risk for severe disease.

Most healthy children with chickenpox recover at home with care to help them feel better while the illness runs its course. Common treatments and supportive care include:

• Acetaminophen, a fever reducer that helps lower temperature and ease discomfort
• Calamine lotion, which can help soothe itchy skin
• Cool baths with baking soda, colloidal oatmeal, or uncooked oatmeal, all of which may reduce itching
• Keeping fingernails trimmed short to prevent scratching and skin infections

Aspirin should not be given to children with chickenpox, as it can cause a rare but serious condition called Reye’s syndrome, which affects the liver and brain. Ibuprofen is also not recommended for chickenpox because of an increased risk of bacterial skin infections.

Doctors may prescribe antiviral medicines, such as acyclovir, for people who are more likely to develop severe illness. These groups include:

• People older than 12
• People with chronic skin or lung diseases
• People receiving long-term steroid or salicylate therapy for other conditions
• Pregnant women
• People with weakened immune systems

Antiviral medicines work best when started as soon as possible, ideally within the first 24 to 48 hours after the rash appears. In some cases, doctors may recommend other treatments, such as varicella-zoster immune globulin, which can prevent infection or reduce symptoms for people who are at high risk for complications and are exposed to chickenpox.

Potential complications from chickenpox most often involve the skin, lungs, brain, and blood, and can sometimes be life-threatening, especially in people at higher risk.

Complications can include:

• Bacterial skin infections, when bacteria infect the blisters or skin, sometimes leading to scarring
• Pneumonia, an infection of the lungs that can cause breathing problems
• Encephalitis, swelling or infection of the brain, which can cause confusion, seizures, or difficulty walking
• Cerebellar ataxia, a problem with balance and coordination due to brain involvement
• Bleeding problems, such as easy bruising or bleeding from the rash
• Bloodstream infections (sepsis), a serious infection that spreads throughout the body
• Dehydration, from not drinking enough fluids due to fever or mouth sores

Some people may need to be hospitalized for these complications. In rare cases, chickenpox can lead to death, even in healthy children and adults.

People should contact a doctor right away if they suspect someone at high risk for complications is exposed to or contracts chickenpox.

Prompt medical care is also called for if anyone with chickenpox develops any of the following symptoms:

• Fever lasting longer than four days or rising above 102°F (38.9°C)
• Rash or skin that becomes very red, warm, tender, or leaks pus, which may mean a bacterial infection
• Trouble waking up, confusion, or unusual behavior, which may indicate brain involvement
• Difficulty walking, stiff neck, or severe headache
• Frequent vomiting, trouble breathing, severe cough, or severe stomach pain
• Rash with bleeding or bruising

Chickenpox can be prevented through vaccination, which is the most effective way to protect against the disease and its complications.

The chickenpox vaccine is recommended for children, adolescents, and adults who have never had chickenpox or the vaccine. Two doses are needed for full protection. The vaccine is very effective, preventing almost all severe cases and about 90% of all cases. Since the vaccine became widely used, chickenpox cases have dropped by 97% in the United States, and hospitalizations and deaths from chickenpox have become rare.

People who get vaccinated and still get chickenpox usually have a much milder illness. The vaccine also helps protect people who cannot be vaccinated, such as those with weakened immune systems, by reducing the spread of the virus in the community.

Other ways to help prevent chickenpox include:

• Avoiding contact with people who have chickenpox or shingles, especially for those at higher risk
• Practicing good hand hygiene, such as washing hands often with soap and water
• Covering coughs and sneezes to prevent spreading the virus

If someone is exposed to chickenpox and is not immune or vaccinated, getting the vaccine or other treatment soon after exposure may prevent the disease or make it less severe.

For most healthy people, the outlook is excellent, and chickenpox clears up on its own without lasting problems.

Most children recover fully within a week, and serious complications rarely occur. The outlook can be different for babies, adults, pregnant women, and people with weakened immune systems, who are more likely to have severe illness or complications. Hospitalizations and deaths from chickenpox still happen, especially in people who are not vaccinated.

Most people who recover from chickenpox are protected for life and do not get the disease again. However, the virus stays in the body and can reactivate later as shingles, especially in older adults or people with weakened immune systems.

Vaccination greatly improves the outlook by preventing most cases and making any illness that does occur much milder.

“What sets Yale Medicine apart is its comprehensive approach to chickenpox care: from prevention through vaccination and education to expert treatment of symptoms and complications when they occur,” says Marietta Vazquez, MD, a Yale Medicine pediatric infectious diseases expert. “Our pediatric and infectious disease specialists work together to ensure patients receive personalized, evidence-based care at every stage.”

This article was medically reviewed in June 2026.