One of the more unusual, though not uncommon, causes of bad breath is tonsilloliths, also known as tonsil stones. These white concretions of food particles and bacteria of the mouth are akin to pearls, in that they form slowly in the folds of living tissue. They are quite different, though, in that they are made by humans, they are masses of living things and they cause powerful halitosis.
A reader from Iowa recently wrote in to CNN's Expert Q&A to ask what tonsil stones are and where they come from. Pediatrician Jennifer Shu responded that they build up in the folds of tonsils.
Tonsils can be especially folded or wrinkly if they are inflamed or infected. A severe bacterial infection can even leave them permanently wrinkled, a condition known as cryptic tonsils.
As particles get stuck in these glands, bacteria begin to feed on the food matter, creating a colony of microorganisms that live on the surface of the stones. These bacteria form a net over the outside of tonsilloliths called a biofilm.
It is this biofilm that gives some bad breath its sulfurous smell, according to a study in the journal Otolaryngology: Head and Neck Surgery.
Eliminating both tonsil stones and their smell is often as easy as gargling with a specialty breath freshening product until the built-up material comes loose.