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.