or fixed drug eruption due to allergy to the medicines. FDE or fixed drug eruption may fade slowly and so may take a long time to go away.Although they resolve spontaneously but an oral antihistamine (eg, hydroxyzine) and a topical corticosteroid may be needed.Please consult a dermatologist as prescription is needed for steroids.
Hope it helps. Take care and please do keep me posted on how you are doing or in case you have additional queries. Kind regards.