Hi there, the rash you are describing does sound like a steroid induced rash. Unless you have had any new change to your usual routine (new detergent, or fabric you are not used to), I would think that this is the cause. If the prednisone is helping for your RA, I would talk to your rheumatologist to see if there is a different medication that can be recommended at this time or perhaps benadryl (diphenhydramine) cream might provide you some symptomatic relief. Hope my answer was helpful to you.