I had a prednisone shot 10 days ago for a severe case of poison oak . 2 days ago, while the poison oak is almost gone, I broke out in a red rash on my arms at first. Now it has spread to most of my body. From research, I understand this is a known side effect of prednisone. Since I had a shot, will this leave soon? Meanwhile, is there a known effective treatment? I am using Sarna (pramoxine hdyrochloride) and hydrocortisone creams. They don t really help.