Contributor: Gordon K. Klintworth
Seborrheic dermatitis (dermatitis seborrheica, seborrhea, seborrheic eczema) is a common idiopathic skin disease.  While not a disease of sebaceous glands this dermatosis typically affects parts of the skin with numerous sebaceous glands (forehead, scalp, external auditory canal, preauricular area, nasolabial folds, presternal region). Macules and papules form usually with scaling and crusting on a erythematous-yellow base that is frequently greasy. Dandruff is common. Mounds of epidermis with parakeratosis are found at the ostia of hair follicles (follicular lipping). Persons infected with human immunodeficiency virus have an increased incidence of seborrheic dermatitis as well as a severe form. An increased incidence of seborrheic dermatitis also occurs in parkinsonism. In infants seborrheic dermatitis can be a feature of  Leiner disease.