Tinea versicolor or pityriasis versicolor is a common skin infection caused by the yeast Malassezia furfur (formerly termed
Pityrosporum ovale). This yeast is normally found on the human skin and only becomes troublesome under certain circumstances, such as a warm and humid environment.
Generally oval or irregularly-shaped spots of 1/4 to 1 inch in diameter, often merging together to form a larger patch.
These spots commonly affect the back, underarm, upper arm, chest, lower legs, and neck.