How To Treat Itchy Rashes On Arms And Leg?

hello dr. my husband was taking tb septran ds fr 4wks aftr his surgery revision amputation...during the 3rd wk of medication..he developed severe itching over his arms n leg..whch has dvlpd into rashes..hv given him allegra 120mg with cetrizen fr 5days bt no relief..he z applying coconut oil on it..kindly advise some trmnt