Steve, what a trip. I have the same problem. I would get something like hives after sweating in them all day? I've found certain colors of leather are worse.
I don't know if you drink gatorade but for me, yellow #5 and red #40 were adding to the problem big time. Those colors are in so many things. Considering our job, I was drinking a few sports drinks a day in the summer heat. The colors build up in your body. Well after my foot swelled up like a balloon, then another day my hand, and then my tongue, I realized there was a real problem.
Luckily an allergist nailed it. Angioedema (hive under the skin). Allergic to tartrazine (yellow 5). Doritos, gummy bears, mountain dew, etc. You name it, I have to watch out. I still eat gummy bears but I take it easy.
The stuff has been banned in parts of Europe.