Hi @Rabbitheadlights
This part of one of your recent posts jumped out at me: "...hundreds of tiny blisters, insanely itchy......then morphs into the massive red patch and begins to crack and bleed and blister"
Thats exactly how my urticaria manifests itself.
Like your poor DH, my original G.P. and dermatologist wanted to treat the symptoms rather than what was causing it in the first place. I should probably add that I was a child when it started and was referred to Great Ormond Street. None of the treatments I was given worked and I was discharged while the urticaria was getting worse.
It's a very long story which I won't bore you with, but to cut it short I had long and exceptionally thorough sets of allergy testing, way way way more detailed than the tests offered by the NHS, which I'd also had.
The private tests obviously picked up the same things as the NHS ones, but I also came away with details of ingredients which are used to make seemingly everyday products that I need to avoid.
One of mine is an ingredient that is commonly used in liquid hand soap. It was a lightbulb moment. My urticaria would be much better after the end of term school holidays; my school used a certain soap that was causing a reaction. I'd improve when I wasn't using that soap (ingredient) at home.
As your DH got better when he was on furlough, I think he's experiencing something similar to me; he's being exposed to 'substances' at work which are causing the reaction that you don't have at home. This could be things your DH is touching, eating or even breathing in (aerosols).
Unfortunately treating the resulting symptoms won't be a permanent solution. I would definitely recommend private detailed allergy testing. It's not easy living with the results (literally need to check every ingredient on every label). I found that after a few years of complete avoidance, I can tolerate some substances which used to cause an instant unpleasant reaction.
I hope your DH is able to recover, it's a miserable condition to deal with, but it is possible to get on top of it 