White Tanning Spots: Tinea Versicolor
White tanning spots could be caused by a skin fungus known has Tinea Versicolor. The tanning itself is not responsible for producing the fungus. The infected skin does not tan, thus people then realize they have a problem.
Treatment can be successful with diligence and patient. However, people should consult with their doctor to rule out any possibilities of cancer or other skin problems.