It doesn't sound like EIA, but I thought I'd throw it out there. About 10% of the people who have Exercise Induced Allergy (or Asthma) get hives/rashes. I am part of that 10%.
My hives are all over, not just in one area, so I don't think that applies, but it's something to check out. I also only get the breathing problems when the temperature outside is either hotter or colder than what my body is used to that day.