Without examination,confirmation of a diagnosis is tough but it can be pityriasis versicolor or pityriasis alba. Pityriasis versicolor is caused by an overgrowth of a yeast fungus and are found mainly on sun
hypopigmented dermatitis.This is a self-limited disorder that usually resolves itself.Severe cases may benefit by Psoralen plus ultraviolet light A photochemotherapy (PUVA).Pityriasis versicolor needs anti fungal medicines.Pls consult a dermatologist so that confirmatory diagnosis can be made.
Hope it helps.Take care and pls do keep me posted if you have any additional queries.Kind regards.