Hello,
Does you son still have his tonsils? From repeated infection, the tonsils can become enlarged and develop small pockets. Cellular debris, food he's eaten, etc. can become entrapped in these pockets developing into lumpy whitish, yellowish curd-like balls. And believe me, they stink to high heaven! The pockets can become a source of infection, too.
I had strep throat and tonsillitus alot when younger and went through this experience. I kept getting re-infected and spent alot of time being very sick. And the white things made my breath smell like p**p!Finally, my tonsils were so enlarged and riddled with holes Dr. took them out when I was 33. No problems since.
Hope this is helpful to you and that your son is feeling better,
J.