I beleive I have the exact same condition however have not been properly diagnosed yet. I have suffered for 5 or 6 years now and was treated for eczema. None of the topicals worked. I have seen allergy specialists and have tried every antihistamine out there. None helped. Then I seen a dermatologist who diagnosed it as atopic dermatitis( eczema) and put me on methotrexate. This worked and I have stayed on it for a year almost all symptoms completely gone. However my last check up he wanted to switch me to dupixent. So we did that and I am about 6 weeks in and my hives and rash is back full on.
The thing is I only really break out when I am in water, cold, hot, at any place in any water. It comes on within about 15 min of exposure and I break out in full hives, legs, arms, chest, back. They stay for about 2 hours then the rash disappears but skin stills burns and is tingling. Like being washed in gas. Then the places where spots were turn to dry flaky spots.
From everything I'm reading it sounds like aquagenic urticaria. I am hoping the dupixent will work eventually but so far no luck. The methotrexate worked but it is chemo and I'd rather not take it forever if there were other options.