Seborrhoeic dermatitis is a common, chronic, inflammatory dermatosis that has a predilection for the scalp, facial creases and large flexures including the ano‐genital area. It affects adults of all ages and often runs a relapsing course. A short‐lived infantile variant is also recognized. The cause is unclear, but increasing evidence supports a pathogenic role for lipophilic Malassezia yeasts, which comprise part of the normal skin microbiome. Most affected individuals are healthy, but seborrhoeic dermatitis may be a presenting feature of HIV infection, so at‐risk individuals should be tested. Treatment is aimed at reducing scalp yeasts and/or the inflammatory response, with topically applied imidazole antifungal drugs, mild potency corticosteroids and calcineurin antagonists.

Keywords seborrhoeic dermatitis, seborrhoeic eczema, dandruff, pityriasis capitis, Malassezia yeasts, inflammatory dermatosis, immunosuppression, human immunodeficiency virus, HIV