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Page: Origins
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Mouth
Though the causes of breath odor are not entirely understood, most unpleasant odors are known to arise from proteins trapped in the mouth which are processed by oral bacteria. There are over 600 types of bacteria found in the average mouth. Several dozens of these can produce high levels of foul odors when incubated in the laboratory.
The most common location for mouth-related halitosis is the tongue. Large quantities of naturally-occurring bacteria are often found on the posterior dorsum of the tongue, where they are relatively undisturbed by normal activity. This part of the tongue is relatively dry and poorly cleansed, and bacterial populations can thrive on remnants of food deposits, dead epithelial cells and postnasal drip. The convoluted microbial structure of the tongue dorsum provides an ideal habitat for anaerobic bacteria, which flourish under a continually-forming tongue coating of food debris, dead cells, postnasal drip and overlying bacteria, living and dead. When left on the tongue, the anaerobic respiration of such bacteria can yield either the putrescent smell of indole, skatole, polyamines, or the "rotten egg" smell of volatile sulfur compounds (VSCs) such as hydrogen sulfide, methyl mercaptan and dimethyl sulfide.
The odors are produced mainly due to the anaerobic breakdown of proteins into individual amino acids, followed by the further breakdown of certain amino acids to produce detectable foul gases. For example, the breakdown of cysteine and methionine produce hydrogen sulfide and methyl mercaptan respectively. Volatile sulfur compounds have been shown to be statistically associated with oral malodor levels, and usually decrease following successful treatment.
Other parts of the mouth may also contribute to the overall odor, but are not as common as the back of the tongue. These locations are, in descending prevalence order: inter-dental and sub-gingival niches, faulty dental work, food-impaction areas in-between the teeth, abscesses and unclean dentures.
Gum Disease
There is some controversy over the role of periodontal diseases in causing bad breath. Whereas bacteria growing below the gumline (subgingival dental plaque) have a foul smell upon removal, several studies reported no statistical correlation between malodor and periodontal parameters.
Nose
The second major source of bad breath is the nose. In this instance, the odor exiting the nostrils has a pungent odor which differs from the oral odor. Nasal odor may be due to sinus infections or foreign bodies.
Tonsils
Putrefaction from the tonsils is generally considered a minor cause of bad breath (contributing to some 3-5% of cases). Although some people (approximately 5% of the population) suffer from small bits of calcified matter in tonsillar crypts (called tonsilloliths), which themselves smell extremely foul when released, they do not necessarily cause bad breath.
Systemic diseases
There are a few systemic (non oral) medical conditions which may cause foul breath odor, but these are extremely infrequent in the general population. Such conditions are:
1. Fetor hepaticus: an example of a rare type of bad breath caused by chronic liver failure.
2. Lower respiratory tract infections (Bronchial and lung infections).
3. Renal infections and Renal failure.
4. Carcinoma.
5. Trimethylaminuria ("Fish odor syndrome").
6. Diabetes mellitus.
7. Metabolic dysfunction.
People suffering from halitosis should not immediately conclude that they suffer from these conditions or diseases just by deducing from the breath odor alone, since these conditions are rare, may not display bad breath at all and will most likely show additional characters, which are more definitive than the breath odor.
Most researchers consider the stomach as a very uncommon source for bad breath (except in belching). The esophagus is a closed and collapsed tube, and continuous flow (in oppose to a simple burp) of gas or putrid substance from the stomach indicates a health problem - such as reflux or a fistula between the stomach and the esophagus - which will demonstrate more serious manifestations than just foul odor.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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