Induction and inhibition of oral malodor

Mol Oral Microbiol. 2019 Jun;34(3):85-96. doi: 10.1111/omi.12259. Epub 2019 Apr 22.


Volatile sulfur compounds (VSCs) such as hydrogen sulfide (H2 S) and methyl mercaptan (CH3 SH) are the main components of oral malodor, and are produced as the end products of the proteolytic processes of oral microorganisms. The main pathway of proteolysis is the metabolism of sulfur-containing amino acids by gram-negative anaerobic bacteria. Gram-positive bacteria may promote VSC production by gram-negative anaerobes by cleaving sugar chains from glycoproteins and thus providing proteins. A large variety of bacteria within the oral microbiota are thought to be involved in the complex phenomenon of halitosis. Oral microbiota associated with a lack of oral malodor, oral microbiota associated with severe and H2 S-dominant oral malodor, and oral microbiota associated with severe and CH3 SH-dominant oral malodor have been distinguished through molecular approaches using the 16S rRNA gene. Pathological halitosis may primarily be addressed through treatment of causative diseases. In all cases, plaque control is the basis of oral malodor control, and dentifrices, mouthwashes, and functional foods play a supplementary role in addition to brushing. Recently, the use of natural ingredients in products tends to be favored due to the increase in antibiotic-resistant strains and the side effects of some chemical ingredients. In addition, probiotics and vaccines are expected to offer new strategies for improving the oral conditions through mechanisms other than antibacterial agents.

Keywords: anaerobic bacteria; gram-positive bacteria; microbiota; oral malodor; volatile sulfur compounds.

Publication types

  • Review

MeSH terms

  • Dental Plaque
  • Gram-Negative Anaerobic Bacteria / metabolism*
  • Gram-Positive Bacteria / metabolism*
  • Halitosis / microbiology*
  • Halitosis / prevention & control*
  • Humans
  • Hydrogen Sulfide
  • RNA, Ribosomal, 16S
  • Sulfhydryl Compounds
  • Sulfur Compounds*
  • Volatile Organic Compounds*


  • RNA, Ribosomal, 16S
  • Sulfhydryl Compounds
  • Sulfur Compounds
  • Volatile Organic Compounds
  • methylmercaptan
  • Hydrogen Sulfide