CausesBy Mayo Clinic staff
Dandruff can have several causes, including:
- Dry skin. Simple dry skin — the kind you get during winter when the air is cold and rooms are overheated — is the most common cause of itchy, flaking dandruff. Flakes from dry skin are generally smaller and less oily than those from other causes of dandruff, and you'll likely have symptoms and signs of dry skin on other parts of the body, such as your legs and arms.
- Irritated, oily skin (seborrheic dermatitis). This condition, one of the most frequent causes of dandruff, is marked by red, greasy skin covered with flaky white or yellow scales. Seborrheic dermatitis may affect not only your scalp, but also other areas rich in oil glands, such as your eyebrows, the sides of your nose and the backs of your ears, your breastbone, your groin area, and sometimes your armpits.
- Not shampooing often enough. If you don't regularly wash your hair, oils and skin cells from your scalp can build up, causing dandruff.
- Psoriasis. This skin disorder causes an accumulation of dead skin cells that form thick, silvery scales. Psoriasis commonly occurs on your knees, elbows and trunk, but it can also affect your scalp. It may be difficult to differentiate from seborrheic dermatitis if only the scalp is involved.
- Eczema. If you have eczema anywhere on your body, it could also be on your scalp, possibly leading to the development of dandruff.
- Sensitivity to hair care products (contact dermatitis). Sometimes sensitivities to certain ingredients in hair care products or hair dyes, especially paraphenylene diamine (PPD), can cause a red, itchy, scaling scalp. Shampooing too often or using too many styling products also may irritate your scalp, causing dandruff.
A yeast-like fungus (malassezia). Malassezia lives on the scalps of most healthy adults without causing problems. But sometimes it grows out of control, feeding on the oils secreted by your hair follicles. This can irritate the skin on your scalp and cause more skin cells to grow. The extra skin cells die and fall off, clumping with oil from your hair and scalp, making them appear white and flaky in your hair or on your clothes. Most often this eruption is identical to or closely resembles seborrheic dermatitis.
Exactly what causes an overgrowth of malassezia isn't known, although having too much oil on your scalp; changes in your hormones; stress; illness; neurological disorders, such as Parkinson's disease; a suppressed immune system; not shampooing often enough; and extra sensitivity to the malassezia fungus may contribute to the development of dandruff.
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- Seborrheic dermatitis. American Osteopathic College of Dermatology. http://www.aocd.org/skin/dermatologic_diseases/seborrheic_dermati.html. Accessed Sept. 28, 2010.
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