Yesterday morning my niece pointed out that there are lines on my back. I thought she was pretending, until I looked in the mirror and saw it to be true. There are about 6 clearly visible red lines running horizontally across the middle of my back. The spacing between each line is perfectly equal, they are completely straight and perfectly parallel. It almost looks as though I laid on my back on top of a hot grill. These lines were not there the day before, and are still here today. At first I thought I had just leaned against something which left an impression, but as they have not gone away, are not indented, and there is nothing around to match the shape, I know this cannot be the reason for their appearance. They don't itch, sting, hurt, or cause any unnatural sensation whatsoever. I would not have known they were there if she hadn't pointed them out to me. I feel perfectly healthy and am not exactly concerned, so much as very confused. What could have caused this, and what might these be?