Hard to say for sure that it's stains, but he only bathes twice a week, so even if there aren't any now, it's only a matter of time.
Sometimes I wonder why he reveals such embarrassing information, but then I remember his spoiled nature, and realize that any time he doesn't have enough forewarning of being made fun of, his brain will insist on running his mouth on and on as if it shouldn't cost him anything, ever, no matter how many times it has been proven wrong. Look how long it took for TIHYDP to make him start dodging games. He's a slower learner than a fucking insect.