Tonsilloliths or tonsillar concretions occur in up to 10% of the population, frequently due to episodes of tonsillitis. While small concretions in the tonsils are common, true tonsilloliths or stones are rare. They commonly occur in young adults and are rare in children.

The mechanism by which these calculi form is subject to debate, though they appear to result from the accumulation of material retained within the crypts, along with the growth of bacteria and fungi – sometimes in association with persistent chronic purulent tonsillitis.

Recently, an association between biofilms and tonsilloliths was shown. Central to the biofilm concept is the assumption that bacteria form a three dimensional structure, dormant bacteria being in the center to serve as a constant nidus of infection. This impermeable structure renders the biofilm immune to antibiotic treatment. By use of confocal microscopy and microelectrodes, biofilms similar to dental biofilms were shown to be present in the tonsillolith, with oxygen respiration at the outer layer of tonsillolith, denitrification toward the middle, and acidification toward the bottom.