The loss of skin cells from the scalp is a normal part of the life cycle of skin cells. However, excessive flaking of the scalp, or dandruff, is a common cosmetic problem experienced by millions of people. Dandruff is not contagious and is normally not a serious problem. Some cases of excessive dandruff accompanied by intense itching and patches of flaky skin on the face or elsewhere are actually a form of eczema referred to as seborrheic eczema.

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. There is also some evidence that dandruff may run in families. Scalp flakiness may also be caused by psoriasis or other skin ailments or infections.