I've just googled this very question and guess what - theoretically is cos I'm thin!! Well my skin is any way..."Exercise produces excessive body heat which needs to be dissipated so that the body can maintain a constant temperature. The body does this by dilating the blood vessels under the skin allowing more blood flow to the surface. The body also produces sweat to further enhance cooling.
Some people have a thinner outer skin (the epidermis), that is why they appear more red than the average people when they exercise. Our lips appear red for the same reason. "
HA!!! So, if any one asks, it's cos I'm thin!! OK
