What Causes Tiny Red Spots After Taking Cefdinir For Shingles?

I have been diagnosed as having shingles.I started with a cold or flu like illness and was prescribed a 10 day course of Cefdinir on March 10th. Soon after starting this, I developed some tiny red dots. After a few days, these turned into welts. I went to the doctors again on the 19th of March. I was then told that I had Shingles and prescribed Prednisone. So far, I have NOT had any blisters. Generally speaking I m feeling better.Could the fact that I was taking the Cefdinir before any rash appeared have kept the illness from developing into a full blown course of Shingles?