What causes tinea versicolor?

Pityrosporum ovale. Tinea versicolor is a common fungal infection of the skin caused by pityrosporum ovale. It usually presents as dark reddish-brown patches on the skin of the back, upper arms, axilla, chest, and neck. The patches sometimes appear lighter than the surrounding skin because they do not tan with sun exposure. Treatment is often with topical antifungals (e.g. Ketoconazole).
Fungus. Tinea versicolor is caused by a fungus. Usually the particular type of fungus involved is malassezia furfur.