Can Imuran Cause Allergic Reaction Like Red Spots On Legs?

I have ulcerative colitis. I am on my last week of a prednisone taper, on 10 mgs a day and will finish Thursday. My GI dr started me on Imuran when I started the prednison. Now that I am down to the low dose, I am starting to get red spots, some small, some large, on my legs. I have had boils on my legs with the colitis but this looks different. Do you think I am having an allergic reaction to the Imuran?