Erythrasma is a common, chronic superficial bacterial infection of the skin caused by Corynebacterium minutissimum. It is characterized by distinct, superficial hyperpigmented or erythematous patches localized to intertriginous areas, especially of the axillae, genitocrural crease, and interdigital web space of the toes. Lesions are often asymptomatic, although pruritus may be present, especially when it affects the genitocrural region. A "disciform" variant (large disc-like lesions) usually occurs outside of intertriginous areas and is associated with type 2 diabetes mellitus. Erythrasma may be acute or chronic. It may be asymptomatic or pruritic.

Obesity, diabetes mellitus, immunosuppression, a history of atopy, and hyperhidrosis are risk factors. All age groups may be affected, but incidence increases with age. The highest incidence is seen in regions of high humidity, especially in the tropics.