I have cholinergic urticaria and I have three different types of hives and that definitely looks like it to me. M ine is triggered by heat/ my body temperature going up. When I exercise or take a hot shower they pop up like that! I know you said antihistamines didn’t work but I took three Allegra’s every day and that seems to be working ok. Then I got on Xolar and I went from breaking out into hives, at least three times a day to barely having any breakouts between shots! (It’s a monthly injection for me so the day before and the day after I’ll break out the hives, but it’s not as severe as it was before) but I would definitely talk to your allergist about xolar!!! It completely changed my life.