Seborrheic dermatitis is a common skin disease that causes a red, scaly, itchy rash, most often in areas where the skin is oily, such as the scalp, ears, eyebrows, eyelids and upper chest, though other areas of the body may be involved.
The terms dandruff, seborrhrea and seborrheic dermatitis are sometimes used interchangeably but refer to different conditions. Dandruff causes scaling on the scalp but no redness. Seborrhea causes oily skin on the scalp and face without redness or scaling. Only seborrheic dermatitis involves all three symptoms.
Doctors believe a yeast-like organism that lives on the skin combined with excess oil production contributes to the development of seborrheic dermatitis. Immune system sensitivity also plays a role. The disease is not the result of poor hygiene.