Chickenpox (varicella) usually can be diagnosed by the appearance of the chickenpox rash. For healthy children, describing the rash over the phone to a health professional (rather than visiting the office) may be all that is needed.

However, some people need to see a health professional when symptoms of chickenpox appear. You are at more risk for complications from chickenpox if you are a teenager, adult (especially if you smoke cigarettes or have a long-term lung disease), or a pregnant woman, or you have an impaired immune system.

If you visit your health professional's office, chickenpox is diagnosed by medical history and physical examination.

Viral tests can determine whether you have immunity against chickenpox. After you are immune, you cannot get chickenpox.

If you have a blistering rash, it can be tested to confirm whether it is caused by the chickenpox virus. This type of testing usually includes examining:

• Skin cells scraped from inside a blister (immunofluorescent staining). Results of this test are available in 1 or 2 hours.
• Fluid from inside a blister (viral culture). Results of the culture are available in 7 to 21 days.

A woman who has chickenpox early in her pregnancy may want to have her fetus checked for birth defects. This can be done with an ultrasound of the fetus.

Early Detection

There is no general screening for immunity against chickenpox at this time. Most people in the United States had chickenpox as children and have immunity against it.

Some people may be required to be tested for chickenpox immunity. These include people who work in hospitals, day care centers, schools, and other areas where chickenpox can easily be passed from one person to another. Many states now require that children entering day care and school have the chickenpox vaccine(What is a PDF document?) unless they have a doctor's diagnosis or blood test results that prove immunity.

If you are more likely to get severely ill from chickenpox or to have complications of chickenpox, you also need to be tested to confirm whether you have ever had chickenpox and have immunity against it. These people include:

• Women who are able to have children. Women who are pregnant or who want to become pregnant should consider being tested to see whether they have chickenpox immunity. Having chickenpox immunity prevents complications of chickenpox during pregnancy.
• People with impaired immune systems.

If you have never had chickenpox and therefore do not have immunity against it, you may choose to get the chickenpox vaccine (varicella vaccine or Varivax). Talk with your health professional about the risks and benefits of the chickenpox vaccine.