MODEL RELEASED. Chickenpox. Face of an 18 month old girl with chickenpox (or varicella). This is a common infectious disease of childhood caused by the varicella-zoster virus. It causes headache and fever followed by eruption of a rash over most of the body. The rash appears in crops and consists of clusters of small, red, itchy spots that become fluid-filled blisters within a few hours. It is rare to have the disease twice, as a childhood attack confers lifelong immunity. While the disease is not serious in children, in adults it can be dangerous. Calamine lotion can be used to relieve itching until the disease clears up.