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Skip Navigation LinksPennsylvania Department of Health > My Health > A-Z Health Topics > A-D > Chickenpox Fact Sheet


Chickenpox is a childhood illness that causes a blister-like rash, itching and fever. Chickenpox is caused by the varicella-zoster virus (VZV). VZV can also cause shingles.
Signs and Symptoms
Chickenpox symptoms include an uncomfortable, blister-like rash, severe itching, high fever, dehydration and headache. The rash appears first on the face, chest and back, but it can spread over the entire body, including the eyelids, inside of the mouth or genital area. There are usually between 250 and 500 itchy blisters.
In unvaccinated children, chickenpox symptoms usually last five to seven days. Illness in vaccinated children is less common. However, if it does occur, the symptoms are usually mild and only last a few days.
Causes and Transmission
Chickenpox is highly infectious and spreads from person to person by direct contact or through the air from an infected person. A person with chickenpox is contagious one to two days before the rash appears and remains contagious until all blisters have formed scabs. It takes from 10 to 21 days after contact with an infected person for someone to develop chickenpox.
Risk Factors
Before the varicella vaccine, most cases of chickenpox occurred in children younger than 15 years old. Now, the biggest risk factor for developing chickenpox is not being vaccinated.
Certain groups of people are more likely to have serious complications from chickenpox, including:
  • Infants;
  • Adolescents;
  • Adults;
  • Pregnant women; and
  • People with weak immune systems, either from other illnesses or medication such as long-term steroids.
While most children recover from chickenpox without any complications, severe secondary bacterial infections can occur. These can occur at many sites of the body, including the skin, tissues under the skin, bone, lungs (pneumonia), joints and the blood. Other serious complications are due directly to the viral infection and include viral pneumonia, bleeding problems and infection of the brain (encephalitis).
Infants born to mothers who are infected with chickenpox during the first or second trimester can develop congenital varicella syndrome, a rare disorder causing abnormalities at birth.  Infants born to mothers who are infected with chickenpox shortly before or after delivery can develop neonatal varicella, a severe illness of chickenpox in newborns. 
Tests and Diagnosis
There are several laboratory tests that health care providers can use to diagnose chickenpox. However, the diagnosis can usually be made based on the appearance of the rash and symptoms.
Acyclovir, an antiviral medicine, is used to treat chickenpox. Acyclovir can help shorten the length and severity of the illness, but, to be effective, it must be started as soon as possible after the rash appears. Thus, people who think they or their children might have chickenpox should call their health care provider as soon as possible to discuss treatment options.
Non-aspirin medications, such as acetaminophen, may help relieve the pain caused by chickenpox. Wet compresses, calamine lotion and colloidal oatmeal baths may help relieve some of the itching.
The best way to prevent chickenpox is to get two doses of the chickenpox vaccine. Most people who get the vaccine will not get chickenpox.
Disease Patterns
Before the varicella vaccine was introduced, each year in the United States, 4 million people became ill with chickenpox, more than 10,000 people were hospitalized, and more than 100 people died. The disease followed yearly cycles, peaking each year in the spring.
Since the vaccine was introduced, chickenpox illness in the United States has decreased by more than 80 percent. Chickenpox illnesses have also decreased in Pennsylvania. Today, there are approximately 800 cases of chickenpox each year and more than 60 percent are among children ages 0 to 9 years old. Most chickenpox outbreaks in Pennsylvania today happen in elementary schools.
This fact sheet provides general information. Please contact your physician for specific clinical information.

Last reviewed/updated: August 2, 2016