Hello,
You have not mentioned your son’s age. 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
on the face.This is a self-limited disorder that usually resolves by adulthood. Severe cases may benefit by Psoralen plus ultraviolet light A photochemotherapy (PUVA).
My sincere advice would be to get it evaluated from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.