When my body heats up in any way, I get small red bumps all over my body, and a big red rash all over my stomache with some white bumps in the red rash. They're gone within 30 minutes to an hour. But it drives me crazy. I can't do anything heat related, I can't socialize. Etc. I'm 17, so as you know teenage years are the best for partying, etc. I have one possible theory, which is this green, gunk stuff, that cakes on to my skin (from what, I don't know.