Suggest Treatment For Rashes On My Knees To Neck

I am off prednisone now for about one week after being on it for 6 weeks. I developed a rash about 10 days ago as I was tapering off. The rash has steadily gotten worse, and flares up even worse at nights. It is from my knees to my neck. This appears to be a normal side effect of prednisone, but how long does it last?