Seborrheic dermatitis is a chronic relapsing inflammatory skin condition characterized by scaling and poorly defined erythematous patches in areas rich in sebaceous glands. It is one of the most frequent skin disorders and may be socially embarrassing. Fungi of the genus Malassezia, lipid-dependent, ubiquitous skin residents, play a pathogenic role. Topical antifungal agents (e.g., ketoconazole) are the mainstay of treatment, and if used intermittently they can maintain remission. The vehicle itself may also play a relevant role. Improvements in diagnostic criteria, severity measures and outcome variables are needed to better design clinical trials and inform clinical practice.