Definition:

Seborrheic dermatitis (SD) is a common inflammatory dermatological disorder. The characteristic symptoms include scaling, erythema, and itching, which occur most often on the scalp, face, chest, back, axilla, and groin. Its incidence peaks during three age periods: in the first three months of life, during puberty, and in adulthood with an apex at 40 to 60 years of age. The cause of SD is unknown and the disease seems to be multifactorial. Malassezia yeasts are considered to play an important role. They cause an inflammatory reaction that seems to be mediated by free fatty acids, released from sebaceous triglycerides by fungal enzymes such as lipases. The lipid layer of Malassezia can also modulate pro-inflammatory cytokine production by keratinocytes. Although it can be associated with human immunodeficiency virus infection and neurologic disease (e.g., cerebrovascular event, Parkinson disease), SD typically occurs in healthy persons. Its prevalence is 1% to 3% in the general population and 34% to 83% in immunocompromised persons. Topical antifungal agents are the first-line therapy for acute and long-term treatment of SD of the face and body. Treatment includes over-the-counter shampoos and topical antifungals, calcineurin inhibitors, and corticosteroids.