A fungal infection that produces patches of discoloured skin on the trunk
Pityriasis versicolor, also called tinea versicolor, is a patchy skin condition caused by a fungus living in the hair follicles of the body. The fungus does not normally produce symptoms, but in hot and humid conditions, when the skin becomes moist, it grows and colonizes the outer layer of skin. If the skin is oily, the fungus is more likely to spread to the surface of the skin. The infection is more common in men, particularly those under the age of 50.
The only symptom is the appearance of painless, discoloured patches on the skin. The upper trunk area, including the neck, chest, shoulders, and back, is usually affected. The patches are:
Of variable size, round, and flat with clearly defined edges.
Pinkish-brown in colour on pale skin, becoming more noticeable if the surrounding skin tans. On dark skin, the patches are pale. In some people, affected areas are darkly pigmented.
Left untreated, the patches may become widespread and persist indefinitely.
Your doctor will probably be able to diagnose pityriasis versicolor from the appearance of the patches. To confirm the presence of the fungus, he or she may shine an ultraviolet light onto the patches, which will fluoresce yellow-green if the fungus is present, and may also take skin scrapings for laboratory analysis.
Treatment usually consists of washing the affected area regularly with an over-the-counter shampoo containing selenium sulphide, an antifungal drug. With thorough treatment, the infection usually clears up in 2–3 weeks, but it may take several more weeks for your skin to return to its normal colour. If you miss a patch of affected skin when applying the shampoo, the infection will recur. In persistent cases, your doctor may prescribe oral antifungal drugs.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.