Dermatology (from the Greek derma, skin) is the branch of medicine that deals with skin and related tissues (hair, nails, sweat glands, etc.). A doctor specializing in dermatology is a dermatologist. Dermatologists are doctors who specialize in the diagnosis and treatment of diseases and cancers of the skin and its adnexa. The first treatise on dermatology, De morbis cutaneis, is attributed to the Forlì physician Girolamo Mercuriali.

The skin is the most extensive organ of the body and obviously the most visible. Although some dermatological diseases only affect the skin, many others are the manifestation of a systemic disorder, which affects various tissues or organs of the body.