Dandruff is a white or grayish scales shed from the scalp. Dandruff is a symptom of a skin disorder, known as seborrheic dermatitis, which is the most common scalp disorder. Its cause is unknown. The disorder appears as irregular reddish patches, which may be sore and itchy, and is usually accompanied by excessive secretion of oil from the sebaceous glands attached to the roots of the hair. The extreme oiliness of the scalp may make the dead skin, or dandruff, that flakes off the irritated patches very greasy. It may also promote an increase in the bacteria and fungi normally present in the hair. When the itchy patches are scratched, these germs may enter the scalp and produce secondary infections. If the condition is severe and persists long enough, gradual permanent loss of the hair may result.
   The best treatment for mild cases of seborrheic dermatitis is frequent washing and brushing of the hair and scalp. Severe seborrheic dermatitis may be treated with sulfur compounds, and germicidal substances are sometimes necessary to stop infections. Chronic cases can be difficult to treat, and a physician should be consulted.