For decades, it was thought that many common dermatological conditions had no relationship to diet. Studies from recent years, however, have made it clear that diet may influence outcome. In this review, the authors focus on conditions for which the role of diet has traditionally been an underappreciated aspect of therapy. In some cases, dietary interventions may influence the course of the skin disease, as in acne. In others, dietary change may serve as one aspect of prevention, such as in skin cancer and aging of the skin. In others, dermatological disease may be linked to systemic disease, and dietary changes may affect health outcomes, as in psoriasis. Lastly, systemic medications prescribed for dermatological disease, such as steroids, are known to raise the risk of other diseases, and dietary change may reduce this risk.