Section 18. Skin Disorders

Chapter 212. Fungal Skin Infections

Topics: Introduction | Ringworm | Candidiasis | Tinea Versicolor

Tinea Versicolor

Tinea versicolor (pityriasis versicolor) is a fungal infection of the topmost layer of the skin causing scaly, discolored patches.

The infection, caused by the yeast Malassezia furfur, is quite common, especially in young adults. It rarely causes pain or itching, but it prevents areas of the skin from tanning, producing patches that are lighter in color than surrounding skin. People with naturally dark skin may notice lighter patches; people with naturally fair skin may get dark or lighter patches. The color depends on how the yeast affect the melanocytes, the cells that make the pigment (see Section 18, Chapter 208). The patches are often on the chest or back and may scale slightly. Over time, small areas can join to form large patches.

Diagnosis and Treatment

Doctors can diagnose tinea versicolor by its appearance. A doctor may use an ultraviolet light to show the infection more clearly or may examine scrapings from the infected area under a microscope to confirm the diagnosis.

Topical antifungal cream such as ketoconazole may be used, as well as terbinafine solution spray. Prescription selenium sulfide shampoo is effective if applied full-strength to the affected areas (including the scalp) at bedtime, left on overnight, and washed off in the morning. Treatment is usually continued for 3 or 4 nights. Alternatively, the shampoo can be applied for 10 minutes a day for 10 days. Prescription ketoconazole shampoo is also effective; it is applied and washed off in 5 minutes. It is used as a single application or daily for 3 days.

Antifungal drugs taken by mouth, such as itraconazole, ketoconazole, or fluconazole, are sometimes used to treat widespread, resistant infection (see Section 17, Chapter 197). However, because these drugs may cause unwanted side effects, topical drugs are usually preferred.

The skin may not regain its normal pigmentation for many months after the infection is gone. Tinea versicolor commonly comes back after successful treatment because the fungus that causes it normally lives on the skin. Therefore, many doctors recommend use of 2.5% selenium sulfide shampoo or ketoconazole shampoo monthly or every other month to prevent recurrences.