What Is Chickenpox? A Plain-Language Guide to the Itchy Blister Rash Caused by the Varicella-Zoster Virus
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
Chickenpox is an illness caused by the varicella-zoster virus that brings an itchy rash of small fluid-filled blisters, appearing 10 to 21 days after exposure. [1] [3] [4] [5] It spreads through contact with the rash or air droplets, starting up to 48 hours before the rash appears. [1] Two doses of varicella vaccine prevent it, and the virus can later cause shingles. [1]
What the research says
Two vaccine doses protect much better than one. A meta-analysis of 66 studies found varicella vaccine effectiveness of 79% for a single dose and 94% for two doses, and 92% effectiveness against moderate or severe illness; protection slightly declined over time (Bolormaa et al., J Korean Med Sci, 2025) [6].
Protection was still high 10 years after two doses. In a Cochrane review of 138 studies (23,480,668 participants), vaccine effectiveness against varicella of any severity after two doses in children aged 11 to 22 months was 95% over 10 years of follow-up, based on one randomized trial of 2,279 children (high-certainty evidence) (Di Pietrantonj et al., Cochrane Database Syst Rev, 2020) [7].
Antivirals only modestly help otherwise healthy children. In a Cochrane review of three trials, acyclovir cut fever by about 1.1 days and reduced the maximum number of lesions by 76, but results were less convincing for itch relief and time to no new lesions, and the authors called its clinical importance in healthy children uncertain (Klassen et al., Cochrane Database Syst Rev, 2005) [8].
What Is Chickenpox?
Chickenpox is an illness caused by the varicella-zoster virus. It brings on an itchy rash with small fluid-filled blisters. [1] The virus spreads easily to people who haven't had the disease or haven't gotten the chickenpox vaccine. [1]
The chickenpox vaccine is a safe way to prevent this illness and the other health issues that can happen with it. Chickenpox used to be a widespread condition, but today the vaccine protects children from it.
The rash breaks out mostly on the face, scalp, chest, and back, with some spots on the arms and legs. [1] The spots quickly fill with a clear fluid, break open, and then turn crusty. [1]
Chickenpox is caused by the varicella-zoster virus, which produces an itchy rash of fluid-filled blisters that spreads easily to people without immunity.
What Does Chickenpox Look and Feel Like?
The itchy rash from chickenpox appears 10 to 21 days after you're exposed to the varicella-zoster virus. [1] [3] [4] [5] The rash often lasts about 5 to 10 days. [1] Other symptoms may appear 1 to 2 days before the rash. [1]
Stage | What happens |
Before the rash (1–2 days prior) | Fever, not wanting to eat, headache, tiredness, and a general feeling of not being well [1] |
Phase 1 | Raised bumps called papules break out over a few days [1] |
Phase 2 | Small fluid-filled blisters called vesicles form in about one day, then break and leak [1] |
Phase 3 | Crusts and scabs cover the broken blisters; scabs most often fall off in 1 to 2 weeks [1] |
New bumps keep showing up for several days. So you may have bumps, blisters, and scabs on the skin at the same time. [1]
The condition is often mild in children with no other health issues. But for some children, the rash covers the whole body. [1] Blisters may also form in places you might not expect. [1]
When Should You Call a Doctor?
If you think you or your child may have chickenpox, contact your healthcare professional's office. To keep from infecting people in the waiting room, tell the staff that you think you or your child may have chickenpox. [1]
How Does Chickenpox Spread?
A virus called varicella-zoster causes chickenpox. The virus can spread through direct contact with the rash. You also can get it when a person with chickenpox coughs or sneezes and you breathe in the air droplets. [1] [4] [5]
The contagious window is longer than many people realize. You can spread the virus to other people for up to 48 hours before the rash appears. [1] And you can keep spreading it until all broken blisters have crusted over. [1] [4]
Chickenpox spreads through direct contact with the rash or through air droplets, and a person can be contagious up to 48 hours before the rash appears.
Who Is Most at Risk?
Not having had chickenpox or the chickenpox vaccine raises your risk of getting the virus. [1] Most people who have had chickenpox or have gotten the vaccine are immune to chickenpox. [1] If you've been vaccinated and still get chickenpox, symptoms are often milder. [1] You may have fewer blisters and mild or no fever. [1] A few people can get chickenpox more than once, but this is rare. [1] [3]
Is Chickenpox Still Serious?
Chickenpox is often mild. But it can be serious and lead to other health issues. [1]
Complication | What it is |
Skin, soft tissue, or bloodstream infection | Infection of the skin, soft tissues, or bloodstream caused by bacteria [1] |
Dehydration | When the body does not have enough water and other fluids [1] |
Pneumonia | An illness in one or both lungs [1] |
Encephalitis | Swelling of the brain [1] |
Toxic shock syndrome | A dangerous complication caused by bacteria [1] |
Reye's syndrome | A condition that causes swelling in the brain and liver; can happen in children and teens who take aspirin during chickenpox [1] |
Who Faces the Highest Risk of Complications?
People who are at higher risk of chickenpox complications include newborns and infants born to people who haven't had chickenpox or the vaccine (this includes children under age 1 who have not yet had the vaccine), adults, pregnant people who haven't had chickenpox, and people who have a condition that lowers their immune system response or take medicines that lower this response. [1] [4]
What Happens if Chickenpox Strikes During Pregnancy?
Low birth weight and limb problems are more common in babies born to women who are infected with chickenpox early in their pregnancies. [1] When a pregnant person catches chickenpox in the week before birth or within a couple of days after giving birth, the baby has a higher risk of getting a life-threatening infection. [1] If you're pregnant and not immune to chickenpox, talk to your health care provider about these risks.
Can Chickenpox Come Back as Shingles?
If you've had chickenpox, you're at risk of a complication called shingles. [1] The varicella-zoster virus stays in your nerve cells after the chickenpox rash goes away. [1] [4] Years later, the virus can turn on again and cause shingles, a painful cluster of blisters. [1] The virus is more likely to come back in older adults and people who have weakened immune systems. [1]
The pain of shingles can last long after the blisters go away, and it can be serious. [1] This lasting pain is called postherpetic neuralgia. [1]
A vaccine against shingles is recommended for people age 50 and older. [1] The vaccine, called Shingrix, also is an option for people age 19 or older with a weakened immune system because of illness or medical treatments. [1] Get Shingrix even if you've already had shingles or you've had the older shingles vaccine called Zostavax. [1]
How Is Chickenpox Diagnosed?
Chickenpox is often diagnosed based on the rash. [2] A healthcare professional may confirm the diagnosis with lab tests. [2] You may have a polymerase chain reaction (PCR) test, which uses a swab of fluid from a chickenpox blister. [2] PCR stands for polymerase chain reaction, a lab method that detects the virus's genetic material in a sample.
How Is Chickenpox Treated?
Treatment for Otherwise Healthy Children
In otherwise healthy children, chickenpox often needs no medical treatment. [2] Some children may be able to take a type of medicine called an antihistamine to calm itching. [2] But mainly, chickenpox clears on its own. [2]
Treatment for People at High Risk of Complications
If you or your child is at high risk of complications, your healthcare professional may suggest antiviral medicine to treat the virus. [2] Acyclovir, valacyclovir (Valtrex), and famciclovir may ease the symptoms of chickenpox. [2] But they work best when given within 24 hours after the rash appears. [2]
Sometimes, a healthcare professional may suggest getting the chickenpox vaccine within five days of being in contact with the virus. [2] This can prevent the illness or help make it milder. [2] The vaccine is for people who don't have other health issues. [2] People who can't have the live vaccine may get varicella-zoster immune globulin within days of being in contact with the virus. [2] Immune globulin is a blood product that contains ready-made antibodies to help fight the virus.
You or your child may get other medicines to treat complications of chickenpox. For instance, antibiotics can treat infected skin and bacterial pneumonia. [2] Antiviral medicine often treats brain swelling, also called encephalitis. It may need to be treated in the hospital. [2]
Treatment situation | What may be used |
Otherwise healthy children | Usually no medical treatment; an antihistamine may calm itching; the illness clears on its own [2] |
High risk of complications | Antiviral medicine such as acyclovir, valacyclovir (Valtrex), or famciclovir; works best within 24 hours of the rash [2] |
Recent exposure (within 5 days) | Chickenpox vaccine, if you have no other health issues [2] |
Can't receive the live vaccine | Varicella-zoster immune globulin within days of contact with the virus [2] |
Complications | Antibiotics for infected skin and bacterial pneumonia; antivirals (often in hospital) for encephalitis [2] |
What Home Care Helps?
These tips may help ease the symptoms of mild chickenpox.
Try not to scratch. Scratching the skin can cause scarring and slow healing. It also can raise the risk that the sores will get infected. [2] Trim fingernails. It also may help to put gloves on children's hands, especially at night. [2]
Relieve the itch and other symptoms. The chickenpox rash can be very itchy. Broken blisters, called vesicles, sometimes sting. For relief of these and other symptoms, you can try:
Home remedy | What it does |
Cool bath with baking soda, aluminum acetate, or uncooked oatmeal | Soothes the rash; colloidal oatmeal (finely ground oatmeal made for soaking) also works [2] |
Calamine lotion | Dabbed on the itchy spots [2] |
Antihistamines such as diphenhydramine (Benadryl) | Calms itching; ask your child's healthcare professional if they're safe for your child [2] |
Acetaminophen (Tylenol, others) | Lowers a mild fever [2] |
Two important medicine warnings. Call your healthcare professional if a fever lasts longer than four days and is higher than 102 degrees Fahrenheit (38.9 degrees Celsius). [2] [3] Don't give aspirin to children and teenagers who have chickenpox. [2] [3] This can lead to a serious condition called Reye's syndrome. [2] Talk with your healthcare professional before giving any nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen (Advil, Motrin IB, others), to someone who has chickenpox. Some studies suggest that this type of medicine may lead to skin infections or tissue damage. [2]
How Can You Prevent Chickenpox?
To help prevent chickenpox, get two doses of the varicella vaccine. [1] [5] If you get chickenpox after having the vaccine, your symptoms may be much milder. [1]
Some people shouldn't get the vaccine, or they should wait. Check with your healthcare professional about whether you should get the vaccine if you have a weakened immune system (this includes people who have HIV or take medicines that lower the immune system response), are allergic to gelatin or the antibiotic neomycin, have cancer or are getting cancer treatment with radiation or medicines, or recently got blood from a donor or other blood products. [1]
Do not get the chickenpox vaccine if you're pregnant. [1] If you want to get the vaccine before pregnancy, don't try to get pregnant until one month after you have the last dose of the vaccine. [1]
How Should You Prepare for Your Appointment?
Call your family healthcare professional if you or your child has symptoms of chickenpox. Here's some information to help you get ready for your appointment. When you call to make the appointment, ask how you or your child can stay away from others in the waiting room.
What You Can Do
Make a list of all your symptoms and when they began, any recent contact with anyone who had chickenpox, key medical information including other health issues and the names and dosages of all medicines, vitamins, and supplements you or your child takes, and questions to ask your healthcare team. In the meantime, rest as much as possible, try not to touch the rash, and wear a face mask over your nose and mouth when you're in public. The chickenpox virus spreads easily until all skin blisters have fully crusted. [2]
Questions to ask about chickenpox may include what the most likely cause of these symptoms is, whether there are other possible causes, what treatment is suggested, how long it will take for symptoms to improve, whether there are self-care steps for symptom relief, how long it will be before your child or you can no longer spread the virus, and how to lower the risk of infecting others.
What to Expect from Your Doctor
Your healthcare professional may ask whether you or your child has had the chickenpox vaccine and how many doses, whether your child is in school or child care, and whether you are pregnant or breastfeeding.
The Bottom Line
Chickenpox is an itchy, blistering illness caused by the varicella-zoster virus. It spreads easily through contact with the rash and through air droplets, sometimes even before the rash appears. For most healthy children it is mild and clears on its own, but it can be serious for newborns, adults, pregnant people, and anyone with a weakened immune system. Two doses of the varicella vaccine are the safest way to prevent it, and the virus that caused it can return years later as shingles. If you suspect chickenpox, call your healthcare provider, use the self-care steps to stay comfortable, and keep the aspirin away.
Take the Next Step
If your child has developed an unexplained itchy rash with fluid-filled blisters, don't wait it out in silence. Call your healthcare professional's office, describe the rash, and ask how to be seen without exposing others in the waiting room. Use the home-care steps in this guide to keep the itching under control, watch for fever warnings, and ask your doctor about catching up on the two-dose vaccine if you or your child is not yet protected.
Frequently Asked Questions
What is chickenpox and what causes it?
Chickenpox is an illness caused by the varicella-zoster virus. It brings on an itchy rash with small fluid-filled blisters, mostly on the face, scalp, chest, and back.
How long after exposure does the rash appear?
The rash appears 10 to 21 days after you're exposed to the varicella-zoster virus. The rash often lasts about 5 to 10 days.
When is a person with chickenpox contagious?
You can spread the virus up to 48 hours before the rash appears, and you can keep spreading it until all broken blisters have crusted over.
Is chickenpox dangerous?
Chickenpox is often mild, but it can be serious. Complications include skin and bloodstream infections, dehydration, pneumonia, brain swelling (encephalitis), toxic shock syndrome, and Reye's syndrome.
Who is at the highest risk of complications?
Newborns and infants of people who haven't had chickenpox or the vaccine, adults, pregnant people who haven't had chickenpox, and people with a weakened immune system.
What home care helps an itchy chickenpox rash?
Cool baths with baking soda, aluminum acetate, or colloidal oatmeal; calamine lotion on the itchy spots; antihistamines after checking with your child's healthcare professional; and acetaminophen for mild fever. Trim nails and consider gloves at night to prevent scratching.
Can children take aspirin or ibuprofen for chickenpox fever?
No aspirin: it can lead to Reye's syndrome, which causes swelling in the brain and liver. Talk with your healthcare professional before giving ibuprofen or other NSAIDs, since some studies suggest they may lead to skin infections or tissue damage.
Can you get chickenpox more than once?
Most people who have had chickenpox or the vaccine are immune. A few people can get chickenpox more than once, but this is rare. If you get it after vaccination, symptoms are usually milder.
What happens to the virus after chickenpox goes away?
The varicella-zoster virus stays in your nerve cells. Years later it can wake up again and cause shingles, a painful cluster of blisters. A shingles vaccine is recommended at age 50 and older.
Is the chickenpox vaccine safe during pregnancy?
No. You should not get the chickenpox vaccine if you're pregnant. If you want the vaccine before pregnancy, wait one month after your last dose before trying to get pregnant.
Related Reading
Content reviewed and produced following the Rinnit editorial framework. Last updated: October 13, 2026.
This content is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
References
Mayo Clinic Staff. Chickenpox: Symptoms and causes. Mayo Clinic. August 4, 2026. https://www.mayoclinic.org/diseases-conditions/chickenpox/symptoms-causes/syc-20351282
Mayo Clinic Staff. Chickenpox: Diagnosis and treatment. Mayo Clinic. August 4, 2026. https://www.mayoclinic.org/diseases-conditions/chickenpox/diagnosis-treatment/drc-20351287
Malek M, Donahue M. Chickenpox (Varicella) in Children: Symptoms, Treatment & Prevention. HealthyChildren.org (American Academy of Pediatrics). Last updated September 22, 2025. https://www.healthychildren.org/English/health-issues/vaccine-preventable-diseases/Pages/Varicella-ChickenPox.aspx
World Health Organization. Chickenpox (questions and answers). World Health Organization. February 4, 2025. https://www.who.int/news-room/questions-and-answers/item/chickenpox
National Foundation for Infectious Diseases. Chickenpox (Varicella). NFID. Updated January 2026. https://www.nfid.org/infectious-disease/chickenpox/
Bolormaa E, Lee YH, Choe YJ, et al. Varicella vaccine effectiveness and duration of protection: a systematic review and meta-analysis. J Korean Med Sci. 2025;40(44):e286. PMID 41250651. https://doi.org/10.3346/jkms.2025.40.e286
Di Pietrantonj C, Rivetti A, Marchione P, et al. Vaccines for measles, mumps, rubella, and varicella in children. Cochrane Database Syst Rev. 2020;4(4):CD004407. PMID 32309885. https://doi.org/10.1002/14651858.CD004407.pub4
Klassen TP, Hartling L, Wiebe N, et al. Acyclovir for treating varicella in otherwise healthy children and adolescents. Cochrane Database Syst Rev. 2005;(4):CD002980. PMID 16235308. https://doi.org/10.1002/14651858.CD002980.pub3
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