I Think My Dog Was Bitten By A Spider Several

I think my dog was bitten by a spider several weeks ago. The vet put her on steroids and antibiotics. She appeared to be getting better, and the steroids have been being weaned down. Now the blistering is reappearing on her nose and chin again. The original incident occurred the 2nd week of May. We are now in the end of July. I am concerned about prolonged steroid use and the possibility of an invalid dx. Many thanks for your input. She is my therapy dog and as such has extra special place in my life.