My son was diagnosed with Urticaria Pigmentosa at 5 months, we have never had any problems from it. He has the brown spot, discoloration. We were told what it was after a biopsy and told to take Benadryl every day, which I stopped after about a month, because is did nothing, he was not itchy. Well, he is 9 now and diagnosed with Leukemia 2 weeks ago. He has had several blood transfusions and now is having an allergic reaction. The red rash is taking on the pattern of the Urticaria. It is very red, spotty and inflamed. Has anyone ever heard of any problems or reactions from blood transfusions and Urticaria?