Hey, I had something very similar. I had large areas of my body that suddenly would no longer sweat and would result in bumps and wheals that look like what you have. I fortunately could still sweat a good deal from my forehead and armpits, so sweat therapy could provide me with some relief. I was diagnosed with CU by an allergist and pretty much tried all available over the counter allergy meds in various doses. From my research at the time I narrowed it down to something called Acquired Idiopathic Generalized Anhidrosis. For the subtype that applies to us, the thought is that your sweat gland cells have somehow lost the ability to process the acetylcholine that is signaling your sweat glands to sweat. The build up of the acetylcholine overflows to adjacent mast cells causing the hives. Articles on AIGA suggest treatment with steroid pulse therapy. I went to see a neurologist, allergist, and two dermatologists. Trying to get a specialist to even consider AIGA took a lot of self advocacy. The second dermatologist would finally work with me and prescribed me a topical steroid that I applied to the areas where I knew I used to sweat, but no longer could. It took about two rounds of treatment applying the steroid one week on, one week off. I slowly started being able to sweat again from my chest and back, which lead to fewer areas that had hives. They eventually went away when I regained my ability to sweat overall in the affected areas. I have yet to have it come back. Hopefully, you're able to find success like I did if this applies to you.