I have had this for 25 years or more... hugs to you, it's such a hassle. I wish I had great words of wisdom, but I don't. I've been to ten or twelve dermatologists and allergists, and they all tell me the same thing. No new advances, good luck and pick your poison. I've been on Atarax (hydroxyzine) for about 20 years. It keeps my symptoms reasonably under wraps, doesn't make me sleepy, and it's very cheap. I take less than one 25mg tab a day.
I still don't know what sets off my hives tho- I've always maintained that the order is itch, scratch, hives.... ie my scratching causes hives not my hives cause scratching, and trying to get a doc to listen is almost impossible, and maybe it doesn't matter. I'm on estrogen right now and it's not making the itching worse, foods don't seem to do it... sometimes I will just be sitting and my neck just itches like crazy- then I get out the Benadryl and hope I don't touch it. People always say "what's wrong with your neck?" Other spots flare up too, just mostly the one place, visible of course! And if I don't take the atarax my whole person itches and flares.
The only thing I have noticed is that in the course of my battle with Hashimoto's, my itching is "better" under control when my thyroid is dialed in low. Good luck...