I get this from time to time, and can't figure out why. I thought it was from something I was eating, but I'm not sure. Usually allergy rashes are red, or itch, or puff up. This is just a weird mottled-looking skin discoloration, it doesn't hurt and doesn't itch. I get it on my inner thighs, inner calves, and inner upper arms. I posted a photo, if anyone has ever seen anything like it.. lemme know!