Extra-oral halitosis: an overview

Halitosis can be subdivided into intra-oral and extra-oral halitosis, depending on the place where it originates. Most reports now agree that the most frequent sources of halitosis exist within the oral cavity and include bacterial reservoirs such as the dorsum of the tongue, saliva and periodontal pockets, where anaerobic bacteria degrade sulfur-containing amino acids to produce the foul smelling volatile sulfur compounds (VSCs), especially hydrogen sulfide (H2S) and methyl mercaptan (CH3SH). Tongue coating is considered to be the most important source of VSCs. Oral malodor can now be treated effectively. Special attention in this overview is given to extra-oral halitosis. Extra-oral halitosis can be subdivided into non-blood-borne halitosis, such as halitosis from the upper respiratory tract including the nose and from the lower respiratory tract, and blood-borne halitosis. The majority of patients with extra-oral halitosis have blood-borne halitosis. Blood-borne halitosis is also frequently caused by odorous VSCs, in particular dimethyl sulfide (CH3SCH3). Extra-oral halitosis, covering about 5–10% of all cases of halitosis, might be a manifestation of a serious disease for which treatment is much more complicated than for intra-oral halitosis. It is therefore of utmost importance to differentiate between intra-oral and extra-oral halitosis. Differences between intra-oral and extra-oral halitosis are discussed extensively. The importance of applying odor characterization of various odorants in halitosis research is also highlighted in this article. The use of the odor index, odor threshold values and simulation of bad breath samples is explained.