I am doing the Couch to 5K program and today I did W5D2, which is 8 minutes running, 5 minutes walking and 8 minutes running. I run on my treadmill, and I did nothing different tonight from any other run. Well, by the time I made it through the first 8 minutes, I had broken into this, for lack of a better word, rash. It was all over my hands, arms, stomach, chest and a small bit on my legs. I spent that 5 minute walk between runs trying to keep myself from scratching my skin off. I made it through the second 8 minutes (yay!) but by the time I was done with the cool down and stretching, I was miserable. Running cool water over it in the shower made it feel better and now, about two hours after I finished running, it is completely gone. So does anyone have any clue what in the world happened? The only thing that I can figure out is that it was a heat rash, but I wasn't any hotter than I normally am. My basement is pretty chilly and I had the fan running on the treadmill so I had a lot of cool. Thoughts?