Volatile Sulfur Compounds as The Cause of Bad Breath: A Review

Bad breath or halitosis is a concern for millions of people. Halitosis is subdivided into intraoral and extraoral halitosis, depending on the place where it originates. About 90% of halitosis originates within the oral cavity and includes bacterial reservoirs such as the dorsum of the tongue, where anaerobic bacteria degrade the sulfur containing amino acids cysteine and methionine into the foul smelling volatile sulfur compounds (VSCs) hydrogen sulfide (H2S) and methyl mercaptan (CH3SH). Tongue coating is considered to be the most important source of VSCs. Intraoral halitosis can be treated effectively by cleaning the tongue with a tongue-scraper and by using special mouthrinses. Extraoral halitosis can be subdivided into non-blood-borne halitosis such as halitosis from the nose and the respiratory tract, and into blood-borne halitosis. The majority of patients with extraoral halitosis have blood-borne halitosis, frequently caused by the odorous VSC dimethyl sulfide (CH3SCH3). Extraoral halitosis, covering about 5-10% of all cases of halitosis, might be a manifestation of a serious disease. It is of utmost importance to differentiate between intraoral and extraoral halitosis, which can easily be done by comparing mouth breath with nose breath. The importance of applying odor characteristics in halitosis research is also highlighted.