Dandruff can have several causes, including:

  • Dry skin. Simple dry skin is the most common cause of 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 your scalp and 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.
  • Other skin conditions. People with skin conditions such as eczema — a chronic, inflammatory skin condition — or psoriasis — a skin condition marked by a rapid buildup of rough, dry, dead skin cells that form thick scales — may appear to have dandruff.
  • A yeast-like fungus (malassezia). Malassezia lives on the scalps of most adults, but for some, it irritates the scalp. This can irritate your scalp and cause more skin cells to grow. The extra skin cells die and fall off, making them appear white and flaky in your hair or on your clothes. Why malassezia irritates some scalps isn't known.
  • Sensitivity to hair care products (contact dermatitis). Sometimes sensitivities to certain ingredients in hair care products or hair dyes, especially paraphenylenediamine, can cause a red, itchy, scaly scalp. Shampooing too often or using too many styling products also may irritate your scalp, causing dandruff.
Jan. 23, 2014