 [ Symptoms ] is sulpher in doxycycline or prednisone  prednisone 20 mg doxycycline hyclate 100 mg my husband took these meds they are finished now but he is haveing an alergic reaction to one of these meds reaction is a rash top of rt shoulder and both arms what should he do [ Disease ] hundreds of different things can cause allergic reaction including the doxycycline but neither has sulfa the prednisone can help fight an allergic reaction an antihistamine may also help