I have the same condition. My general doctor referred me to an allergist/immunologist, and I was told that I have autoimmune urticaria (hives). I was prescribed an antihistamine (Zyrtec), Zantac75 (an antacid that also has "alpha blocker" properties), and Doxepin (an antidepressant that also has "alpha blocker" properties. Over time, I stopped taking the Zyrtec and Zantac. Now I am only taking the Doxepin. This seems to control everything pretty well. My doctor also told me about Plaquenil, which was a medication for lupus patients but also works well with my condition. However, the Plaquenil is known for some side effects that could lead to retinal spotting, so regular eye exams are required and he recommends not taking it for extensive periods of time. I hope this helps!
What test were done? And where are the hives located?