Dr. Greene’s Answer:
Tinea versicolor is a mild, superficial fungal infection, somewhat similar to ringworm (true ringworm can also result in white patches). Since the affected skin doesn’t change color well with sun exposure, it usually becomes apparent as white patches during the summer months. In the winter it may seem to disappear, or even seem to become slightly darkened patches as the surrounding skin gets paler (this is where the name versicolor comes from).
Tinea versicolor is most common in adolescents and young adults 15 to 30 years old (although it can certainly happen at any age). The infection is chronic and recurs easily, but it causes no other health problems. People are most susceptible to the fungus during hot months in humid areas. Taking steroids, excessive sweating, wearing tight-fitting clothing, and chronic illness can all predispose a person to tinea versicolor, but someone without any of these factors can still get this mild infection.
The patches of tinea versicolor can appear white, tan, or pink. The white patches look very similar to pityriasis alba. There are two good ways to tell them apart.
The most reliable way is to have a doctor gently scrape the white patch, dissolve the scrapings in potassium hydroxide, and look at what is left under a microscope. The classic “spaghetti-and-meatball” appearance of budding yeast confirms the diagnosis of tinea versicolor. A quicker and easier approach is to look at the patches under a black light. The patches of tinea versicolor will usually light up with a blue-white, yellow, or orange color.
Topical antifungal medicines are very effective for treating tinea versicolor, but there is a more convenient, less expensive, highly effective alternative. Selenium shampoos are great at getting rid of the fungus. Simply apply a thin layer over the affected skin before bed (with a wide surrounding margin, since it may already be beginning to spread). Wash thoroughly the next morning.
The problem is that no matter what the treatment, it comes back easily. Whatever treatment is used for tinea versicolor, all bedding and nightclothes should be changed after treatment to prevent recurrence. Also, re-treating once a week for 3-4 weeks and then once a month for 3-4 months makes it much less likely to come back.
Even when the condition is effectively treated, the white patches will remain for a while. At least several weeks must pass for the newly healthy skin to adjust its color to the amount of ongoing sunlight exposure, so that it will match the surrounding skin.