The highly contagious chicken pox is transmitted by droplets or direct contact, and the developing spots are the first manifestation of the varicella virus infection. After an incubation period of 8–21 days fever occurs and red itchy bumps appear in phases over several days. At the beginning there is a red papule which develops into a vesicle with an initially clear and afterwards cloudy fluid. The vesicle breaks and leaves a crust. The intensity of the exanthem can vary considerably. It has to be assumed that contagion lasts from one to two days prior to the appearance of the rash until five days after the last appearance of vesicles. Complications mainly concern immunocompromised persons. Superinfections of scratched vesicles, pneumonia and central nervous system effects (in most cases an inflammation of the cerebellum) have to be mentioned. If a severe infection is expected, a virustatic drug (aciclovir ) can be administered. The varicella-zoster-virus remains dormant in sensomotor ganglia and can be reactivated later in life as shingles (herpes zoster ). The most important preventative measure of chicken pox is active varicella‐vaccination (immunization, active).