A case of oral foreign-body granuloma due to diatoms.

Diatoms are photosynthetic algae with a siliceous exoskeleton. Diatoms are utilized by a wide array of industries for applications such as filtration and pest control. Unsubstantiated claims have also propelled their societal reach to trendy oral and topical uses. This case highlights a rare case of an oral granuloma secondary to diatoms. An 80-year-old woman presented with a mobile, firm, asymptomatic submucosal mass on her lower left mandibular vestibular mucosa. Histopathology showed a non-caseating granulomatous reaction to diatoms. Her only verified contact with a diatomaceous earth product was a dental impression using alginate after upper front teeth trauma 5 months before. Although there have been several cases of allergic contact dermatitis attributed to diatoms, there are no reported cases of diatom-induced granuloma formation found in the literature. There are, however, ample data on granulomas initiated by silica. Given the silica-based composition of diatoms, and the broad use of diatoms in industry and alternative medicine, it is unclear why diatom-induced granulomas are not more widely described. This report may alert clinicians to the existence of diatom granulomas and incline them to tailor their history to cover questions about possible exposure when evaluating patients presenting with a localized oral lesion.