One such example is a condition known as tinea versicolor, a superficial yeast infection that produces white
spots on the skin
that are difficult to remove.
Some of the perceived causes are emotional stress, hereditary factors, worms, sunburns and physical illness. This skin condition can be aggravated due to diseases like hyperthyroidism, diabetes mellitus, pernicious anemia and Addison's disease.
You should talk to your doctor and rule out the above causes.