(See also Evaluation of the Dental Patient Evaluation of the Dental Patient The first routine dental examination should take place by age 1 year or when the first tooth erupts. Subsequent evaluations should take place at 6-month intervals or whenever symptoms develop... read more 
.)
Pathophysiology of Halitosis
Halitosis most often results from fermentation of food particles by anaerobic gram-negative bacteria in the mouth, producing volatile sulfur compounds such as hydrogen sulfide and methyl mercaptan. Causative bacteria may be present in areas of periodontal disease Periodontitis Periodontitis is a chronic inflammatory oral disease that progressively destroys the tooth-supporting apparatus. It usually manifests as a worsening of gingivitis and then, if untreated, with... read more 
, particularly when ulceration or necrosis is present. The causative organisms reside deep in periodontal pockets around teeth. In patients with healthy periodontal tissue, these bacteria may proliferate on the dorsal posterior tongue.
Factors contributing to the overgrowth of causative bacteria include decreased salivary flow Xerostomia Xerostomia is dry mouth caused by reduced or absent flow of saliva. This condition can result in discomfort, interfere with speech and swallowing, make wearing dentures difficult, cause halitosis... read more (eg, due to parotid disease, Sjögren syndrome Sjögren Syndrome Sjögren syndrome is a relatively common chronic, autoimmune, systemic, inflammatory disorder of unknown cause. It is characterized by dryness of the mouth, eyes, and other mucous membranes due... read more 
, or use of anticholinergic drugs), salivary stagnation, and increased salivary pH.
Certain foods or spices, after digestion, release the odor of that substance to the lungs; the exhaled odor may be unpleasant to others. For example, the odor of garlic is noted on the breath by others 2 or 3 hours after consumption, long after it is gone from the mouth.
Etiology of Halitosis
About 85% of cases result from oral conditions. A variety of systemic and extraoral conditions account for the remainder (see table Some Causes of Halitosis Some Causes of Halitosis Halitosis is a frequent or persistent unpleasant breath odor. (See also Evaluation of the Dental Patient.) Halitosis most often results from fermentation of food particles by anaerobic gram-negative... read more ).
The most common causes overall are the following:
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Gingival disorders Gingivitis Gingivitis is a type of periodontal disease characterized by inflammation of the gums (gingivae), causing bleeding with swelling, redness, exudate, a change of normal contours, and, occasionally... read more
or periodontal disease Periodontitis Periodontitis is a chronic inflammatory oral disease that progressively destroys the tooth-supporting apparatus. It usually manifests as a worsening of gingivitis and then, if untreated, with... read more -
Smoking
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Ingested foods that have a volatile component
Gastrointestinal disorders rarely cause halitosis because the esophagus is normally collapsed. It is a fallacy that breath odor reflects the state of digestion and bowel function.
Other breath odors
Several systemic diseases produce volatile substances detectable on the breath, although not the particularly foul, pungent odors typically considered halitosis. Diabetic ketoacidosis Diabetic Ketoacidosis (DKA) Diabetic ketoacidosis (DKA) is an acute metabolic complication of diabetes characterized by hyperglycemia, hyperketonemia, and metabolic acidosis. Hyperglycemia causes an osmotic diuresis with... read more (DKA) produces a sweet or fruity odor of acetone, liver failure Acute Liver Failure Acute liver failure is caused most often by drugs and hepatitis viruses. Cardinal manifestations are jaundice, coagulopathy, and encephalopathy. Diagnosis is clinical. Treatment is mainly supportive... read more produces a mousy or sometimes faintly sulfurous odor, and renal failure Acute Kidney Injury (AKI) Acute kidney injury is a rapid decrease in renal function over days to weeks, causing an accumulation of nitrogenous products in the blood (azotemia) with or without reduction in amount of urine... read more produces an odor of urine or ammonia.
Evaluation of Halitosis
History
History of present illness should ascertain duration and severity of halitosis (including whether other people have noticed or complained), adequacy of the patient’s oral hygiene, and the relationship of halitosis to ingestion of causative foods (see table Some Causes of Halitosis Some Causes of Halitosis Halitosis is a frequent or persistent unpleasant breath odor. (See also Evaluation of the Dental Patient.) Halitosis most often results from fermentation of food particles by anaerobic gram-negative... read more ).
Review of systems should seek symptoms of causative disorders, including nasal discharge and face or head pain (sinusitis Sinusitis Sinusitis is inflammation of the paranasal sinuses due to viral, bacterial, or fungal infections or allergic reactions. Symptoms include nasal obstruction and congestion, purulent rhinorrhea... read more 
, nasal foreign body Nasal Foreign Bodies Nasal foreign bodies are found occasionally in young children, the intellectually impaired, and psychiatric patients. Common objects pushed into the nose include cotton, paper, pebbles, beads... read more ), productive cough and fevers (pulmonary infection), and regurgitation of undigested food when lying down or bending over (Zenker diverticulum Esophageal Diverticula An esophageal diverticulum is an outpouching of mucosa through the muscular layer of the esophagus. It can be asymptomatic or cause dysphagia and regurgitation. Diagnosis is made by barium swallow... read more 
). Predisposing factors such as dry mouth, dry eyes, or both (Sjögren syndrome Sjögren Syndrome Sjögren syndrome is a relatively common chronic, autoimmune, systemic, inflammatory disorder of unknown cause. It is characterized by dryness of the mouth, eyes, and other mucous membranes due... read more ) should be noted.
Past medical history should ask about duration and amount of use of alcohol and tobacco. Drug history should specifically ask about use of drugs that can cause dry mouth (eg, those with anticholinergic effects—see table Some Causes of Xerostomia Some Causes of Xerostomia Xerostomia is dry mouth caused by reduced or absent flow of saliva. This condition can result in discomfort, interfere with speech and swallowing, make wearing dentures difficult, cause halitosis... read more ).
Physical examination
Vital signs are reviewed, particularly for presence of fever.
The nose is examined for discharge and foreign body.
The mouth is examined for signs of periodontal disease Periodontitis Periodontitis is a chronic inflammatory oral disease that progressively destroys the tooth-supporting apparatus. It usually manifests as a worsening of gingivitis and then, if untreated, with... read more , dental infection Toothache and Infection Pain in and around the teeth is a common problem, particularly among patients with poor oral hygiene. Pain may be constant, felt after stimulation (eg, heat, cold, sweet food or drink, chewing... read more 
, and cancer. Signs of apparent dryness are noted (eg, whether the mucosa is dry, sticky, or moist, and whether saliva is foamy, stringy, or normal in appearance).
The pharynx is examined for signs of infection and cancer.
Sniff test
A sniff test of exhaled air is conducted. In general, oral causes of halitosis result in a putrefying, pungent smell, whereas systemic conditions result in a more subtle, abnormal odor. Ideally, for 48 hours before the examination, the patient avoids eating garlic or onions, and for 2 hours before, the patient abstains from eating, chewing, drinking, gargling, rinsing, or smoking. During the test, the patient exhales 10 cm away from the examiner’s nose, first through the mouth and then with the mouth closed. Malodor that is perceived as worse through the mouth suggests an oral etiology; malodor that is perceived as worse through the nose suggests a nasal or sinus etiology. Similar malodor through both nose and mouth may suggest a systemic or pulmonary cause.
If site of origin is unclear, the posterior tongue is scraped with a plastic spoon. After 5 seconds, the spoon is sniffed 5 cm from the examiner’s nose; a bad odor suggests the malodor is caused by bacteria on the tongue.
Red flags
Interpretation of findings
Because oral causes are by far the most common, any visible oral disease may be presumed to be the cause of halitosis in patients with no extraoral symptoms or signs, and a dentist should be consulted. When other disorders are involved, clinical findings often suggest a diagnosis (see table Some Causes of Halitosis Some Causes of Halitosis Halitosis is a frequent or persistent unpleasant breath odor. (See also Evaluation of the Dental Patient.) Halitosis most often results from fermentation of food particles by anaerobic gram-negative... read more ).
In patients whose symptoms seem to be related to intake of certain food or drink and who have no other findings, a trial of avoidance (followed by a sniff test) may clarify the diagnosis.
Testing
Extensive diagnostic evaluation should not be undertaken unless the history and physical examination suggest an underlying disease (see table Some Causes of Halitosis Some Causes of Halitosis Halitosis is a frequent or persistent unpleasant breath odor. (See also Evaluation of the Dental Patient.) Halitosis most often results from fermentation of food particles by anaerobic gram-negative... read more ). Portable sulfur monitors, gas chromatography, and chemical tests of tongue scrapings are available but best left to research protocols or to specific dental offices that focus on halitosis evaluation and treatment.
Treatment of Halitosis
Underlying diseases are treated.
If the cause is oral, the patient should see a dentist for professional cleaning and treatment of gingival disease Gingivitis Gingivitis is a type of periodontal disease characterized by inflammation of the gums (gingivae), causing bleeding with swelling, redness, exudate, a change of normal contours, and, occasionally... read more and caries Caries Caries is tooth decay, commonly called cavities. The symptoms—tender, painful teeth—appear late. Diagnosis is based on inspection, probing of the enamel surface with a fine metal instrument... read more 
. Home treatment involves enhanced oral hygiene, including thorough flossing, toothbrushing, and brushing of the tongue with the toothbrush or a scraper. Mouthwashes are of limited benefit, but some with oxidant formulations (typically containing chlorine dioxide) have shown greater short-term success. If the patient has a history of alcohol abuse, nonalcoholic mouthwashes should be used. Psychogenic halitosis may require psychiatric consultation.
Geriatrics Essentials
Older patients are more likely to take drugs that cause dry mouth, which leads to difficulties with oral hygiene (as do limited manual dexterity and conditions such as rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease that primarily involves the joints. RA causes damage mediated by cytokines, chemokines, and metalloproteases. Characteristically... read more 
and Parkinson disease Parkinson Disease Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more ) and hence to halitosis, but they are otherwise not more likely to have halitosis. Also, oral cancers are more common with aging and are more of a concern among older than younger patients.
Key Points
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Most halitosis results from fermentation of food particles by anaerobic gram-negative bacteria that reside around the teeth and on the dorsum of the tongue.
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Extraoral disorders may cause halitosis but are often accompanied by suggestive findings.
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It is a fallacy that breath odor reflects the state of digestion and bowel function.
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Mouthwashes provide only brief benefit.
