with your descriptions it seems that you are having focal vitiligo or chemical leucoderma due to footwear. it is primarily an autoimmune disease with a familial predisposition presented with chalky white or milky white in appearance. other autoimmune diseases may be associated like pernicious anemia diabetes alopecia areata (patchy hair loss) and thyroid disorder. so you need to do blood sugar t3 t4 and tsh (thyroid stimulating hormone). i suggest ointment tacrolimus 0. 1% during night hours and mometasone 0. 1% cream in the daytime for six months or may be more depending on your response to the treatment. revert back after a month to a dermatologist online --> <link>
is leucoderma curable?