I turned bright red from scalp to ankles, and itchy has hell, then I started fainting. Nothing like the surprise of suddenly finding yourself on the floor with no idea how you got there...
Turns out when you're bright red for too long, too much of your blood is on the surface of your body and so you get low blood pressure. Too low blood pressure = fainting.
Luckily I was only in the hospital a half-day, but I get so skittish about going that I packed a ton of stuff. Better safe than sorry!
Enough medical stuff, body.