Seborrhoeic dermatitis of the scalp is characterised by varying degrees of scaling, inflammation, exudation and crusting affecting the scalp. It may occur in isolation or may be accompanied by seborrhoeic dermatitis of other sites. It may be difficult to differentiate from scalp psoriasis. Pityriasis capitis (dandruff) is considered to represent a mild form of seborrhoeic dermatitis of the scalp.