Test Your Knowledge

Dandruff is a common and often chronic (ongoing) condition that is characterized by excessive shedding of dead skin cells from the scalp (skin that covers the top portion of the head). The medical term for dandruff is pityriasis simplex capillitii. Dandruff flakes appear as dry, white or grayish, emerging as small patches on top of the head. The condition is not contagious.

Skin is composed of three layers: the epidermis, dermis and subcutaneous tissue. The outer protective layer of skin is the epidermis. The middle layer is the dermis, which contains blood vessels, glands and nerve endings. The bottom layer is the subcutaneous tissue, which contains fat, nerves and blood vessels.

The outermost layer of the skin, the epidermis renews itself about once a month. Dead cells are continuously moving from the deepest layer of the epidermis to the skin’s surface, where they die. Usually the scalp sheds these dead cells unobtrusively. When people have dandruff, skin cell turnover becomes unusually rapid and the excess dead scalp cells are more visible as flakes.

Dandruff differs from two other skin conditions, seborrheic dermatitis and psoriasis. Both conditions are more severe and may involve other areas of the body besides the scalp. In seborrheic dermatitis, inflammation and itching (pruritus) accompany the flaky scales. Psoriasis is an inflammatory skin disease that features thicker flakes that keep piling up atop the scalp. Dry skin and contact dermatitis (resulting from irritating hair products) may also cause excessive scaling of the skin.

Dandruff usually begins during puberty and is common throughout adolescence and young adulthood. Typically, it peaks around age 40. However, older adults may also experience it. For some people, dandruff can be a lifelong nuisance.

Generally, dandruff is uncommon in children younger than age 10. In children, the scaly flakes are more likely the result of a fungal infection called scalp ringworm (tinea capitis). Unlike dandruff, ringworm usually causes a red, inflamed scalp as well as hair loss.