What Is Chickenpox?
Medically reviewed by Jonathan B. Jassey, DO
The varicella-zoster virus causes chickenpox. It is a highly contagious disease that leads to an itchy rash, fever, and fluid-filled blisters. Chickenpox primarily affects children under age 12, but adults can also get it.
Chickenpox is a mild illness that clears up after a week or two. However, it can be severe, especially for pregnant people, babies, and those with a weakened immune system.
This article reviews everything you need to know about chickenpox.
What Causes Chickenpox?
Varicella-zoster is the virus that causes chickenpox. While anyone can get chickenpox, it is most common in children under 12.
Chickenpox is highly contagious and spreads from person to person. You can get it from respiratory droplets when someone coughs, sneezes, or through direct contact. Direct contact means touching the chickenpox sore or a contaminated object and then your mouth or nose.
A person is immune if they have had chickenpox or the vaccine. Nonimmune people are those who have not had chickenpox or the vaccine. If someone gets chickenpox, up to 90% of the nonimmune people close to that person will get the infection.
Chickenpox Symptoms
Chickenpox symptoms usually appear within 10 to 21 days after exposure. The most classic symptom of chickenpox is an itchy rash that turns into fluid-filled blisters. Chickenpox can cause 200–500 blisters to develop over the body.
Initially, a chickenpox rash looks like red, itchy bumps on the face, chest, and back. It then spreads to other body parts, including the mouth, eyelids, or genital area.
The itchy bumps turn into fluid-filled blisters that are almost see-through. Once the blisters break, the sores start to scab over and heal.
Blisters develop in waves. As some start to heal and crust over, new spots can appear. Because of this, some describe the pattern or look of the rash as a “starry sky.”
Other symptoms may be flu-like symptoms such as:
A fever
Fatigue (really tired)
Malaise (feeling unwell)
Muscle aches
Sore throat, runny nose, cough
Headache
Mpox (Monkeypox) vs. Chickenpox
Mpox (formerly referred to as monkeypox) and chickenpox are different viral infections that cause similar symptoms, including a rash that turns into blisters. The following is a comparison of how they differ.
Mpox
Rare
Caused by the monkeypox virus
Transmitted from animals to people
Rash typically stays on the face, arms, and legs
Chickenpox
Very common and contagious
Caused by the varicella-zoster virus
Transmitted from person to person
Rash is widespread on the body
Stages of Chickenpox: Symptom Progression
Chickenpox has four distinct stages, each has its own set of symptoms.
Stage 1 (Incubation)
The first stage of chickenpox (incubation) lasts 10 to 21 days. This is when the virus enters the body and starts to spread, but there are no symptoms.
Stage 2 (Prodromal)
The second (prodromal) stage lasts for one to two days. During this phase, a person may have cold or flu-like symptoms such as a fever, sore throat, headache, loss of appetite, and fatigue.
Flu-like symptoms are more common in adults than children. The rash is frequently the first symptom for kids.
A person is contagious and can spread the virus to others during this stage.
Stage 3 (Active)
The third stage is the active stage, when the characteristic chickenpox rash appears. It usually starts as red bumps on the face, chest, and back and then spreads to the rest of the body.
The rash develops into fluid-filled blisters. After a few days, the sores crust over and eventually fall off.
While a person is most contagious during this time, they can transmit it during all phases. This stage usually lasts about four to seven days.
Stage 4 (Recovery)
The final stage of chickenpox is the recovery stage. It typically lasts about one to two weeks. As the blisters heal, they can cause itching and discomfort.
The varicella virus causes both chickenpox and shingles, but there are key differences in their presentation. The following summarizes the key differences:
Chickenpox is the primary infection (when a person gets varicella for the first time).
After someone has chickenpox, the varicella virus stays dormant in the body.
People get shingles when the varicella virus reactivates.
The shingles rash is usually on one side of the body and is more painful than chickenpox.
Shingles typically occurs in older adults or people with weakened immune systems.
How Long Is Chickenpox Contagious?
You're contagious with chickenpox from one to two days before the rash appears until all the blisters have crusted over. You are most contagious during the two days before the rash through the first several days of the rash.
If you have had the vaccine and develop a mild case of chickenpox, you may have sores that don’t crust over. In this case, you are contagious until you have not developed any new sores for 24 hours.
Experts recommend quarantining (avoiding contact with others) until all the blisters have crusted over. Because the blisters come in waves, it typically takes 10 to 14 days for this to occur.
Quarantining helps prevent the spread of the virus to others, which is especially important for those at higher risk for complications (pregnant people, newborns, and people with weakened immune systems).
Those with shingles can spread the virus to someone who has not had chickenpox or has not had the vaccine. However, that person will get chickenpox, not shingles.
When caring for someone with chickenpox, you can take extra precautions to help prevent the spread, including:
Washing your hands frequently (for 20 seconds or more)
Not scratching (this can break blisters, and the fluid is contagious)
Not sharing personal items
Disinfecting surfaces
Getting a postexposure vaccination (if you are not immune)
Wearing an N95 mask (especially for those at high risk)
Related:Can You Get Chicken Pox Twice?
How Is Chickenpox Diagnosed?
Healthcare providers typically diagnose chickenpox by its characteristic symptoms and rash. In some cases, a provider may order the following lab tests to confirm the diagnosis:
Polymerase chain reaction (PCR) test (using a small sample of the fluid in the blister)
Blood tests
Culture (blister fluid is put in a petri dish in the lab to see what grows)
They may also ask you questions or run tests to rule out other conditions that can cause similar symptoms, including:
Other viral infections (herpes, enterovirus)
Drug reaction
Erythema multiforme (skin disorder from drug reaction)
Rickettsialpox rash (disease spread by mites)
Scabies (skin infestation from mites)
Impetigo (bacterial skin infection)
Insect bites
Chickenpox Treatment
Chickenpox typically clears up on its own within a few weeks. Most of the time, treatment involves easing the symptoms such as itching and discomfort.
You can keep the itch down by:
Keeping cool (being in an air-conditioned room, applying cool clothes to the skin)
Soaking in a lukewarm bath with uncooked oatmeal or baking soda
Applying calamine lotion over the blisters
Taking an oral antihistamine, such as Benadryl (diphenhydramine) or Zyrtec (cetrizine)
You can also try nonaspirin over-the-counter (OTC) fever and pain medications. The American Academy of Pediatrics recommends Tylenol (acetaminophen) rather than Advil and Motrin (ibuprofen).
Do not give children aspirin unless it is under the direction and supervision of a healthcare provider (this would only occur in rare situations). Aspirin can cause Reye's syndrome in kids. Reye's syndrome is a serious illness that affects the liver and brain.
Healthcare providers may prescribe antiviral medications such as Zovirax (acyclovir) for those with severe cases or weakened immune systems. Antivirals can help reduce the severity, duration, and risk of complications.
Healthcare providers may also suggest varicella-zoster immune globulin infusions for those who can not have the vaccine and are at high risk.
Complications From Chickenpox
While chickenpox is usually a mild illness in children, it can be more severe for people:
Over 12 years old
Under 1 year old
With weakened immune systems (lower ability to fight germs)
Who are pregnant
The most common complications of the varicella virus include bacterial infections and pneumonia.
Children
Children with chickenpox are most at risk for bacterial infections of the skin and soft tissues. They are also susceptible to dehydration.
Adults
Adults who get varicella are most at risk of developing pneumonia. Rare but serious complications also include:
Cerebellar ataxia (loss of muscle coordination)
Encephalitis (brain infection or inflammation)
Hemorrhagic (bleeding) conditions
Complications of bacterial infections (sepsis, toxic shock syndrome, osteomyelitis)
Pregnant people who get chickenpox are at higher risk of getting pneumonia. If they have varicella in the first trimester or early second trimester, the baby could have congenital abnormalities, including scars, abnormal legs or arms, brain or eye problems, and low birth weight.
Chickenpox Vaccine
In the United States, chickenpox was much more common before the vaccine. About 4 million people got chickenpox in the early 1990s before the vaccine became available in 1995.
Chickenpox rates decreased by more than 97% in the United States over the past 25 years. The Centers for Disease Control and Prevention (CDC) estimates the chickenpox vaccine has prevented 91 million cases since then.
The CDC recommends two doses of the chickenpox vaccine for those who have not had chickenpox or the vaccine.
Children typically get their first dose between 12 and 25 months and their second dose between four and six. Second doses can be given earlier, but it needs to be at least three months after the first dose.
The vaccination is also crucial for:
Teachers and childcare workers
Healthcare professionals
Those who care for people with weak immune systems
People who live or work in correctional facilities
Those in the military
International travelers
Teens and adults that live with younger children
People who can or may become pregnant
You do not need a vaccination if you already have immunity against varicella, such as if you have already had the disease.
Outlook
Most people with chickenpox recover fully and avoid serious complications. However, it can cause complications such as pneumonia and bacterial infections in some cases.
The best way to prevent chickenpox is to get the vaccine. In the United States, rates have decreased by 97% since the vaccination program began in 1995.
Healthcare providers may suggest antivirals or immunoglobulin infusions to those at high risk and who can not get the vaccination, including babies, pregnant people, and those with weakened immune systems.
