Could be his feet, or it could be that the detergent you are using is not cleaning the clothes well enough, or the temp setting you're using??? Some bacteria and other organisms can survive a regular wash cycle. Try washing his clothes in hot water, and on the highest dryer setting, have him take a shower and give him the clothes and see if he still smells. If he does, I would suspect some weird medical thing. If he doesn't, then at least you know it's probably the clothes, or his sweat/oil after a few hours...which could also signal a weird medical issue [I don't mean it is necessarily bad..but maybe his sweat/oil glands produce something a little different than other people?]. Also, how long does he go in between washing his bedsheets/comforters, how old is the mattress he is sleeping on? Maybe it's mold or a fungus or something?