Do you have patches of skin that are darker or lighter than the skin around them? Do you experience any mild itching in the discolored areas? If so, you may have a condition called tinea versicolor. It’s also frequently called pityriasis versicolor and is caused by a naturally occurring yeast that lives on the skin. Normally, the yeast doesn’t cause any harm, but if it grows out of control, it can cause tinea versicolor. Certain treatments, including tinea versicolor shampoo, may help minimize symptoms of the condition.