Can I Be Allergic to Prednisone?

MY foot had a case of contact dermatitis for bout 2 weeks, so the doctor prescribed me Prednisone pills. I was instructed to take 6 pills once a day with food for first 4 days and decrease to 4 pills the next 4 days. After taking 3 days of Prednisone, I wake up covered from head to toe with itchy red rashes. I have no known allergies to anything untill now. But the only thing is Prednisone is used to treat allergic reactions, so how could that be?