Seborrhea: A chronic inflammatory disease of the skin characterized by the accumulation of scales of greasy skin. There may be yellow crusted patches that are itchy. Seborrhea often affects the scalp. Other sites include the face, ears, eyebrows and eyelids, umbilicus, and genitalia, Seborrhea of the scalp is commonly known as dandruff.

Treatment is with gentle washing, avoiding the use of harsh or perfumed soaps that can further irritate the oil glands. Coal-tar soap and similar preparations may also be useful.

Seborrhea has been said to be an allergy to yeast on the skin but this has not been proved. Also called seborrheic dermatitis.