There are different causes of white spots on the skin. The location, time of onset, and associated symptoms help in the diagnosis. Any new skin spots should be examined by a skin doctor
(a dermatologist) for the proper diagnosis and treatment plan. While there are many causes of white spots, the white spots you are describing could be a skin condition called tinea versicolor which is due to a kind of fungus. Tinea versicolor is not contagious and it is not dangerous. It typically occurs on the shoulders, upper chest, as well as on the back and stomach. Tinea versicolor is typically asymptomatic though sometimes it can be itchy. The fungus that causes tinea versicolor is very commonly found on human skin and for unknown reasons some people react to it and the fungus is able to sustain itself, producing a product that causes the white spots to be seen on the skin. The fungus thrives in hot temperatures. Although not dangerous, it causes discoloration of the skin and for this reason many people will choose to seek treatment for it by seeing a dermatologist. Other causes of white spots include vitiligo, mycosis fungoides, hereditary skin depigmentation diseases, as well as other forms of inflammatory and infectious skin conditions.