I Had A Total Knee Replacement And The Wound Became

I had a total knee replacement and the wound became infected. My doc ordered Silver Sulfadiane evem thought I told him I had a severe reaction to a Sulfa anti-biotic. I was told to Never use sulfa again. I used one small amount on the incision and now have a very red and itchy rash. It is spreading around my leg and I have not scratched it. Please help!