A sebaceous gland is a small gland in the skin which secretes sebum, a fatty substance that acts as a protective and water repellant layer on skin and allows the epidermis to retain its suppleness. Sebum also contains some antibacterial substances. Sebum secretion is fairly constant but varies from individual to individual. Obstructed sebaceous glands become blackheads which are the basis for acne.

Seborrhea is a disorder of the sebaceous glands characterized by over-production of sebum that results in red, scaly patches on the skin and dandruff. Common at puberty, it predisposes to dandruff.