Cure for red skin rash and accompanying hair loss following surgery on Weimaraner.?

My two year old female Weimaraner had a double surgery at the beginning of March for spaying following accidental mating and for removal of a benign tumour on her flank. The cut for spaying healed well but the cut on her flank was followed by a red rash, heavy flaking with partchy loss of hair in the surrounding area. Three months later the problem not only continues but has spread and the affeced area is oval shaped, about 10 inches in length and 5 inches in width. She has been treated with Enrocin, Wysolone and now withThyroxin following a blood test which showed hypothyroidism. Anitibiotic, antifungal and cortisone based ointments have been regularly applied. The dog is least bothered about the rash and it causes no itching. The red rash is patchy over the area described. The flaking has come down, the hair growht has improved, but not the rash. She is a beautiful Weimaraner and I am very sad that the Vet and I have been unable to help her recover.