What Is The Treatment For Skin Hives?

My husband has been having hives for almost 3 month now. At first He was put on prednisone which helped, but once he was donewith the prescription, turbines came back. Then more prednisone. After this prescription he had severe abdominal pains which resulted in appendectomy. The next day he was covered in hives wordethan before. They thought it was due prescription pain medication and switched him a couple times. They sent him home with more prednisone. He has gone to an dermatologist andan allergist. He was not allergic to anything, so blood work was ordered. The only thing that came back out of the normal range was bilirubin. It was reported as slightly elevated. He was referred to a gastrointestinal specialist who has run more blood work looking forliver issues. We are waiting on the follow-up appt. In the mean Filene has been given 2 more rounds of prednisone. The very next day of the last dose the hives return. Do you have any suggestions or ideas of what could be causing this