Spotty skin? holidays ? help?

heat rash? When I went to my friend's cottage last summer, I laid out in the sun for like a couple hours on a really hot day, and then my whole body (except my face) was covered in bumps, they were red-hot and from afar looked like a bad sunburn, up close they were just raised red bumps everywhere! could that be it? I had the bumps for four days, but if you stay out of the sun it'll get better