Seborrheic dermatitis is a rash with greasy, flaky skin patches. The patches can look whitish. With lighter skin, the skin under the patches can look reddish. With darker skin, the skin can also look darker or lighter than the usual skin colour.

The rash may appear on many parts of the body. On the scalp, dandruff is the mildest and most common form of it. In young babies, the greasy patches on the scalp are called cradle cap. Babies may also get the rash in the diaper area. People of all ages may get these patches on the scalp, face (especially the eyebrow area and near the nose and mouth), ears, underarms, or genital area or under the breasts.

Seborrheic dermatitis in teens and adults can be treated with antifungal shampoos and medicines put on the skin. Cradle cap in babies usually goes away without treatment within a few weeks to several months.