Seborrheic dermatitis is an inflammatory disease in areas rich in sebaceous glands, usually the scalp, face, and postauricular, presternal, and intertriginous areas. It may be localized or disseminated. It has a bimodal distribution, with peaks at ages 2-12 months (infantile seborrheic dermatitis) and in adolescence and early adulthood.

Infantile seborrheic dermatitis usually manifests in the second week of life and lasts 4-6 months. It has no racial / ethnic or sex predilection. It characteristically presents on the face, diaper area, and folds of the neck and axillae.

The pathophysiology of infantile seborrheic dermatitis is not well known. However, many factors have been postulated to influence its development. Maternal androgens, transferred to the baby in utero, are thought to result in overactive sebaceous gland activity. In addition, the yeast Malassezia has been implicated.