The patches are dry with very fine scales. These are completely benign, similar to a mild form of eczema. They are most common in children with dry skin. The involved patches don't darken with sun exposure the way the surrounding skin does. Sometimes topical steroid creams help.
Some people get pityriasis alba every summer during childhood.
Even then, the pigmentation will eventually end up normal. The other extremely common white-patch condition is called tinea versicolor. Since the affected skin doesn't change color well with sun exposure, it usually becomes apparent as white patches during the summer months. The infection is chronic and recurs easily, but it causes no other health problems. People are most susceptible to the fungus during hot months in humid areas.