How Should Reoccurring Neck And Body Sunburn Rash Be Treated?

I was taking Prednisone 40 mg a day for 6 days when I developed a horrible sunburn like rash on my neck, which spread over my body in pink dots. I was told to stop it, which I did. The rash went away. Now, 10 days later, the rash is back with a vengeance, but I've not taken anything. I feel horrible and extremely weak. Any advice??