Trichomycosis and erythrasma in the armpit of a 70 year old white female patient. Both are caused by infection with Corynebacterium sp. bacteria. Trichomycosis is an infection of the hairs, where the bacteria form a film over the hair. It is usually asymptomatic. Erythrasma causes pink or brown patches on the skin, most often in the armpits, groin, or between the toes. Treatment is with topical antiseptics or antibiotics.