Tinea versicolor is a common skin infection caused by yeast, a type of fungus, that normally live on the skin. When the yeast proliferates rapidly, it can cause a rash that appears as either pink, tan or white spots. Because the yeast feeds on skin oils, it is most commonly seen on the back and chest, where may oil glands live. Tinea versicolor is more common in teenagers and young adults with oily skin. It is also more common in tropical environments and in the summer when sweating is more common.
It is unclear why the tinea yeast overgrows in some people, but it is not contagious and not harmful. Occasionally, the rash itches, and it can be treated with topical antifungals. Once cleared it has the tendency to come back, so maintenance therapy may be recommended.