This could be tinea versicolor which presents with pale oval or irregularly-shaped spots
which affect the back, underarm, upper arm, chest
, lower legs, and neck. It is caused by a type of yeast that are normally found on the human skin and can proliferate in conditions such as warm and humid environment. Over-the-counter topical antifungal medications may help. If it persists, have this evaluated further for proper stronger prescription medication.