Most children with chickenpox act sick, with symptoms such as a fever, headache, tummy ache, or loss of appetite for a day or two before breaking out in the classic pox rash. These symptoms last 2 to 4 days after breaking out.

The average child develops 250 to 500 small, itchy, fluid-filled blisters over red spots on the skin.

• The blisters often appear first on the face, trunk, or scalp and spread from there. Appearance of the small blisters on the scalp usually confirms the diagnosis.
• After a day or two, the blisters become cloudy and then scab. Meanwhile, new crops of blisters spring up in groups. The pox often appear in the mouth, in the vagina, and on the eyelids.
• Children with skin problems such as eczema may get more than 1,500 pox.

Most pox will not leave scars unless they become infected with bacteria from scratching.

Some children who have had the vaccine will still develop a mild case of chickenpox. They usually recover much more quickly and have only a few pox (less than 30). These cases are often harder to diagnose. However, these children can still spread chieckenpox to others.

Chickenpox is usually diagnosed from the classic rash and the child's medical history. Blood tests, and tests of the pox blisters themselves, can confirm the diagnosis if there is any question.