What is Pityriasis versicolor?

Pityriasis versicolor is a common fungal skin condition caused by an overgrowth of yeast that naturally lives on the skin. It causes patches of skin that are lighter or darker than the surrounding area, most often on the chest, back, and shoulders.

It's more noticeable in warm, humid weather or after sun exposure, since affected patches don't tan in the same way as unaffected skin. It's not contagious and is generally harmless, though it can affect confidence due to its visible appearance.