Chickenpox is a mild but highly infectious condition caused by a virus called the varicella-zoster virus (varicella is the medical name for chickenpox). It causes an itchy rash that blisters and then crusts over.

How common is chickenpox?

Chickenpox is most common in children under 10 years of age, although it can develop at any age. It is most common to catch chickenpox in winter and spring, particularly between March and May.

Chickenpox is so common in childhood that 90% of adults who grew up in the UK are immune (resistant) to the condition because they have had it before.


After a chickenpox infection, the virus remains dormant (inactive) in the body’s nerve tissues. At any time later in life, but usually as an adult, the virus can be reactivated and cause a different form of the virus, known as shingles.


Chickenpox occurs in approximately three in every 1,000 pregnancies and can cause serious complications for both the pregnant women and her baby.

It is possible to develop shingles during pregnancy, but this should not affect the baby in any way.


There is no cure for chickenpox, although there are some measures that can relieve the symptoms, such as painkillers and calamine lotion. In most people, the blisters crust up and fall off naturally within one to two weeks.

Chickenpox can be a more serious infection in:

  • pregnant women
  • newborn babies
  • people with a weakened immune system

These people should seek medical advice as soon as they are exposed to the chickenpox virus.

Chickenpox is most infectious from one to two days before the rash starts until around five days after the rash starts. Children should stay home from school and adults should stay off work until the condition is no longer infectious.

After having chickenpox, it is rare to catch chickenpox for a second time. This is because the body develops immunity to the chickenpox virus, which stops someone from becoming re-infected.