A guy I went to school with who's a Doctor now wrote a paper on various forms of moist and dry heat as well as cooling through the introduction of wet towels, dry hot towels and chemical gels that retained heat or cold. He basically found that it only confuses the body.

I think he found that three of his "subjects" (Fellow friends. Myself included.) ended up getting symptoms of heat exhaustion quicker than the average because skin temp went down, but core temperature went up in response to the cooling of the skin. In the end you end up twice as hot twice as quick. You end up sweating eitherway.

Twenty years after the first "Cold Climate Vest" was made for those twin boys who were born without sweat glands they (Johns Hopkins, I believe) found that there is no real way to properly control the cooling/warming of the human body in a safe and productive way.