(See also Overview of Fungal Skin Infections.)
The infection is caused by Malassezia furfur and is quite common, especially among young adults. Malassezia furfur is a type of fungus that can exist as both a yeast and a mold. Yeast and mold are terms that are used to describe what the fungus looks like under a microscope.
Malassezia furfur is typically harmless and normally lives on the skin but in some people causes tinea versicolor. Most affected people are healthy. Some people may be genetically predisposed to overgrowth of this fungus.
Other risk factors for tinea versicolor include heat and humidity and an immune system weakened by corticosteroid use, pregnancy, undernutrition, diabetes, or other disorders.
Tinea versicolor is a mild infection and is not considered contagious.
Tinea versicolor usually does not cause symptoms. However, it does cause many tan, brown, salmon, or white scaly patches to appear on the trunk, neck, abdomen, and occasionally the face. The patches may join to form larger patches. The patches do not tan, so in summer, when the surrounding skin tans, the patches may become obvious. People with naturally dark skin may notice lighter patches. People with naturally fair skin may get darker or lighter patches.
Doctors diagnose tinea versicolor by the appearance of the skin and by looking at skin scrapings under a microscope to see the fungus.
Doctors may use an ultraviolet light (called a Wood light) to show the infection on the skin more clearly.
Any antifungal drugs applied directly to the affected areas (topical) may be used to treat tinea versicolor. Prescription-strength selenium sulfide shampoo is effective if applied to affected skin (not just the scalp) for 10 minutes a day for 1 week or for one 24-hour application each week for one month. Other treatments include applying topical ketoconazole daily for 2 weeks and bathing with zinc pyrithione soap or applying sulfur-salicylic shampoo to the skin daily for 1 to 2 weeks. (See also table Some Antifungal Drugs Applied to the Skin (Topical Drugs).)
Antifungal drugs taken by mouth, such as fluconazole, are sometimes used to treat people who have a widespread infection (see Table: Drugs for Serious Fungal Infections) or frequent infections.
To lower the chance of the infection coming back, many doctors recommend practicing meticulous hygiene and using zinc pyrithione soap regularly or one of the other topical treatments monthly.