Dandruff is believed to be related to a fungus known as Malassezia (formerly termed pityrosporum) that lives on the scalp of most people. In some cases, overgrowth of the fungus results in the flakiness of the skin characteristic of dandruff. The reasons for the overgrowth of fungus are unclear but may be related to increased oil production, hormonal changes, stress, neurologic disorders such as Parkinson's disease, recovery from chronic conditions such as stroke or heart attack, suppression of the immune system, and infrequent shampooing.
Quick GuideFight Dandruff: How to Treat, Control, and Prevent Flakes
- Dandruff is produced when the skin of the scalp exfoliates excessively.
- The white dusty flakes of material in the hair and on the shoulders are fragments of the superficial stratum corneum.
- Lack of shampooing can enhance dandruff by allowing flakes to accumulate on the hair.
- There are a number of scalp diseases than can produce dandruff.
What is dandruff? What causes dandruff?
The most common cause of dandruff is seborrheic dermatitis (seborrhea), which tends to occur on the scalp, ears, face, mid-chest, and mid-back. The cause of seborrhea is unknown, although a yeast that often lives on the skin, Malassezia furfur, may play a role.
A common secondary manifestation of seborrhea of the scalp is dandruff. Seborrhea produces plaques of itchy dermatitis with scaling. It is the accumulated scale that we call dandruff. Reddish, scaly plaques may also appear in the eyebrows, on the forehead, in the ear canal, on the folds of skin that extend from the nostril to the commissure of the lips. Although skin affected by seborrhea may feel and look dry, this is not the case; moisturizers are of little help in its control.
Scalp seborrhea does not cause permanent hair loss. Often, scalp seborrhea doesn't even itch significantly. Seborrhea can appear during infancy, starting shortly after birth and lasting several months. It may affect the scalp ("cradle cap") or produce scaly plaques on the body. Seborrhea may occur at any age.
Some people who have weakened immune systems, such as those on chemotherapy or those with HIV disease or certain neurological disorders, may have very severe seborrhea. It is important to emphasize, however, that seborrhea is a very common condition, affecting perhaps 5% of the population (with men predominating). The vast majority of those who have it are completely healthy and have no internal or immune problems.
There are a variety of other inflammatory diseases that can produce excessive scaling and therefore dandruff, including psoriasis, fungal infection of the scalp skin (tinea capitis), and allergic contact dermatitis.
Medically Reviewed by a Doctor on 4/21/2015