There could be number of causes for white patches on face like leucoderma, pityriasis alba
, seborrheic dermatitis
, PMLE(sun allergy
), any other eczema. As the previous doctor had suggested sun screen, might be your son had polymorphous light eruption(PMLE). So ask him to avoid sun exposure, use sunscreen daily and also apply steroid cream like mometasone cream twice in a day for few days. At the same time, I would still encourage you to visit a dermatologist
as this recent onset of white lesions could be due to any of the causes mentioned above. Take care.