Chickenpox is a highly contagious disease that causes an itchy red rash of spots or blisters (called pox) that usually appear on the face, scalp, and trunk. It is caused by an infection of the varicella [var-uh-sel-uh] zoster virus and despite its name, has nothing to do with chickens.

Chickenpox usually occurs in children 12 and under but people of any age can contract it. The older that a person is when they are first exposed to chickenpox, the more severe it will be. Once a person has been infected with varicella, they are unlikely to get it again. However, the varicella virus may remain dormant in the body for decades and there is a possibility that the infection may resurface at a later time as a different type of skin condition called shingles.