INTRODUCTION — Halitosis (from the Latin word for breath, “halitus”; also known as oral malodor, “fetor ex ore,” or “fetor oris”) is a common condition. Patients may not be aware of their own bad breath and learn of it from another person.
This topic will cover the epidemiology, pathogenesis, causes, evaluation, and management of halitosis. Related topics such as gingivitis, periodontitis, and odontogenic infections are discussed elsewhere. (See "Overview of gingivitis and periodontitis in adults" and "Gingivitis and periodontitis in children and adolescents" and "Epidemiology, pathogenesis, and clinical manifestations of odontogenic infections" and "Complications, diagnosis, and treatment of odontogenic infections".)
●Halitosis – Halitosis is defined as “malodor with intensity beyond a socially acceptable level perceived” [1,2]. It is a significant concern for many individuals and may negatively affect their quality of life and personal relationships .
●Physiologic halitosis – Bad breath that does not have a specific cause. It is usually worse in the morning and often transient.
●Pathologic halitosis – Bad breath that results from a specific identifiable cause.
●Pseudo-halitosis – Perception by the patient that bad breath is present when there is no objective evidence of bad breath.
•Halitophobia – A type of pseudo-halitosis in which the patient has persistent distress about bad breath despite a negative evaluation by a clinician.
EPIDEMIOLOGY — The prevalence of halitosis is estimated to be up to 32 percent . The majority of the studies on the epidemiology of bad breath are small and focus on self-reported halitosis, which limits the validity . Most of the people affected are not aware of having halitosis .
Bad breath affects all ages, including children, although it is more commonly seen in the adult population [7,8]. Males and females are equally affected.
In addition, approximately 25 percent of the patients seeing a health care professional for a complaint of bad breath do not have true halitosis (the so-called "halitophobics") [6,9,10].
PATHOGENESIS — The majority of cases of halitosis (80 to 90 percent) arise from intraoral causes . Oral malodor is associated with poor oral hygiene and periodontal disease (gingivitis and periodontitis), although individuals without such disorders may also experience halitosis . Bad breath is predominantly caused by bacterial action on material between the teeth and debris on the dorsum of the posterior one-third of the tongue . The tongue is particularly important, as the crevices and fissures provide a favorable environment for the growth of odor-causing bacteria. Dry mouth, defective dental restorations, odontogenic abscess, and unclean dentures may also contribute to bad breath .
The primary microorganisms implicated in the etiology of halitosis are Gram-negative anaerobes, which include Bacteroides forsythus, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Treponema denticola, Tannerella forsythensis, Porphyromonas endodontalis, and Eubacterium spp. Gram-positive microorganisms may also be involved in the production of malodor by deglycosylating glycoproteins that are subsequently broken down by proteolytic enzymes secreted by the Gram-negative bacteria [15,16]. Solobacterium moorei is a Gram-positive bacterium that is associated with oral malodor [17,18].
Bacteria involved in the pathogenesis of bad breath release malodorous chemicals. Volatile sulphur compounds (VSCs), such as hydrogen sulfide, methyl mercaptan, and dimethyl sulfide, are especially important. VSCs arise via microbial degradation of methionine and cysteine . Other gases that are byproducts of amino acid degradation and may be implicated in the pathogenesis of bad breath include indole and skatole (via breakdown of tryptophan), cadaverine (via breakdown of lysine), putrescine, and short-chain fatty acids (butyric, valeric, and propionic) [20,21].
CAUSES OF HALITOSIS — Halitosis can be classified as physiologic, pathologic, or subjective (table 1).
Physiologic — Physiologic halitosis commonly occurs in the morning as a result of relatively low flow of saliva. It results from the action of bacteria on desquamated epithelial cells and entrapped food particles on the dorsum of the tongue. It may be more prominent with lack of attention to personal oral hygiene. It usually resolves immediately after brushing, flossing, eating, and/or drinking water.
Other causes of temporary halitosis include tobacco smoking and consumption of aromatic food (eg, garlic, onions) and certain beverages (eg, alcohol, coffee) .
Pathologic — Pathologic causes of halitosis can be categorized according to the anatomic site of origin (table 1). Malignant tumors, a rare cause of halitosis, can arise from multiple anatomic sites, including the oral cavity, nasal cavity, oropharynx, nasopharynx, hypopharynx, larynx, trachea, and esophagus.
Oral — Pathology within the mouth is the most common identifiable cause of halitosis. When pathology in the mouth is producing halitosis, an observer will find the greatest odor coming from the mouth rather than the nose.
Oral causes of halitosis include the following:
●Periodontal infections harbor Gram-negative bacteria that produce volatile sulfur compounds (VSCs). (See "Overview of gingivitis and periodontitis in adults" and "Complications, diagnosis, and treatment of odontogenic infections".)
●Halitosis can originate from the teeth in patients with significant caries or food particles trapped between teeth.
●Excessive tongue coating can cause halitosis. In contrast to physiologic halitosis, halitosis from excessive tongue coating does not improve substantially as the day progresses. A strongly malodorous tongue scraping suggests that excessive tongue coating is the cause of the halitosis. (See 'Organoleptic tests' below.)
●Dry mouth is associated with halitosis, as the lack of salivary flow compromises the antimicrobial action of the saliva, leading to more bacteria within the mouth and increased plaque on the teeth and coating on the tongue. Many medications can cause dry mouth, including diuretics, antihistamines and decongestants, tricyclic antidepressants, and amphetamines.
●Tonsillar pathology accounts for a small percentage of cases .
•Patients with chronic caseous tonsillitis may have retention and/or discharge of cheese-like, whitish material from the crypts with associated malodor. Over time, this material mineralizes to form tonsilloliths (ie, tonsil stones). Tonsilloliths are strongly associated with high levels of VSCs because of the presence of anaerobic bacteria including Eubacterium, Fusobacterium, Porphyromonas, Prevotella, Selenomonas, and Tannerella spp [23,24].
•Peritonsillar abscess also can cause bad breath. (See "Peritonsillar cellulitis and abscess", section on 'Typical presentation'.)
●Less common causes of halitosis arising from the mouth include inadequately cleaned dentures and tumors with necrosis. (See "Oral lesions", section on 'Oral squamous cell carcinoma'.)
Nasal — When halitosis has a nasal cause, the odor detected with nasal exhalation will be greater than that from oral exhalation. (See 'Organoleptic tests' below.)
Nasal causes of halitosis include:
●Acute or chronic sinusitis
●Postnasal drip, which can cause bad breath if the drip is putrefied by the tongue microbiota
●Foreign bodies in the nose, usually seen in children, which are an uncommon cause of halitosis
Respiratory — Pulmonary infections, such as bronchitis, bronchiectasis, or lung abscess, are rare causes of halitosis (table 1).
Gastroesophageal — Uncommonly, halitosis can originate from a gastrointestinal source. Odorant volatiles may be released from the stomach through the esophagus and the mouth and cause bad breath.
●Helicobacter pylori infection (not well established)
●Gastroesophageal reflux disease (GERD) (not well established)
Systemic — With systemic causes of halitosis, the intensity of the odor from the mouth and the nose is similar.
●Advanced kidney disease
●Advanced liver disease (fetor hepaticus)
●Trimethylaminuria, a rare genetic condition characterized by a fishy odor in breath, sweat, and urine
Subjective — Subjective halitosis (also called pseudo-halitosis) is defined as a complaint of bad breath without objective confirmation and can be categorized as psychologic or neurologic.
Psychologic causes of halitosis include monosymptomatic hypochondriacal psychosis and olfactory reference syndrome [10,34]. Some patients who have been treated for objective bad breath develop psychologic halitosis once bad breath is under control .
Halitophobia is a type of pseudo-halitosis in which the patient has persistent distress about bad breath despite a negative evaluation by a clinician. Patients with halitophobia are often obsessed with oral hygiene and brush their teeth multiple times a day and frequently rinse or gargle. They often are convinced that their problem is organic and may resist consultation with a mental health provider .
In the neurologic variant of subjective halitosis, taste or smell disorders (dysgeusia and dysosmia) cause the patient to perceive bad breath when it is not objectively present . Dysgeusia may be a manifestation of hyposalivation, vitamin and mineral deficiencies, nerve injuries, neurodegenerative diseases, and drugs. Dysosmia is commonly associated with allergies and other inflammatory disorders, infections, trauma, and neurodegenerative diseases. (See "Taste and olfactory disorders in adults: Anatomy and etiology".)
Overview — The evaluation of bad breath is often done by dentists or dental hygienists, but a patient may complain to their primary care clinician about bad breath. A useful approach is to consider these questions:
●Does the patient have bad breath by clinician examination?
The odor at the time of examination may not accurately reflect what is typical for the patient. Bad breath can vary with the time of day; it is worse upon waking when salivary flow is relatively low . In patients with periodontitis, it also may be worse during the ovulation phase of the menstrual cycle due to increased levels of Prevotella intermedia and volatile sulfur compounds (VSCs) [19,36,37].
Breath odor also may be affected by oral hygiene, smoking, eating or drinking, and concomitant antibiotic use. If the visit is scheduled specifically for evaluation of bad breath, patients should be advised to refrain from oral hygiene procedures (eg, brushing teeth, using mouth rinse), using tobacco products, eating, drinking, or chewing gum for three hours before the appointment. Patients who are taking antibiotics should be rescheduled.
●If so, is there an identifiable cause that can be treated by the primary care clinician (table 1)?
●If the cause cannot be treated by the primary care clinician, the patient should be referred to the appropriate specialist (dentist, mental health provider, neurologist) (See 'Indications for referral' below.)
History — The evaluation of a patient with a chief complaint of halitosis should begin with a thorough medical and dental history. The clinician should assess oral hygiene practices; whether the patient is mouth breather, snores, or has excess nasal discharge or obstruction; as well as assess for any potentially contributory underlying systemic medical condition. The patient should be asked where they think the malodor is coming from and why. Patients with halitosis often have difficulty assessing their disorder in an objective manner and typically ask family members or friends for a confirmation [6,20].
Physical examination — It is important to do a physical examination of the patient’s mouth, pharynx, and nose. Specific areas of attention include:
●Tongue – Is there significant coating present?
●Dentition – Are the teeth in good repair?
●Gingivae – Is there evidence of gingivitis (eg, gingival redness, swelling, and bleeding provoked by brushing, or flossing) or periodontal disease (eg, tooth mobility)? (See "Overview of gingivitis and periodontitis in adults".)
●Oral mucosa – Are there any lesions suspicious for advanced neoplasia present (eg, persistent oral papules, plaques, erosions, ulcers, or pigmented lesions)? (See "Oral lesions".)
●Tonsils – Is there evidence of tonsillitis, tonsilloliths, or peritonsillar abscess (picture 1A-B)? (See "Peritonsillar cellulitis and abscess", section on 'Typical presentation'.)
●Nose – Is there purulent discharge or a foreign body? (See "Diagnosis and management of intranasal foreign bodies".)
Testing — There are two types of tests typically performed by dentists for the evaluation of halitosis: organoleptic tests and instrumental tests [38,39].
Organoleptic tests — Organoleptic testing is an assessment of the strength of bad breath by a clinician. The clinician assesses the intensity of odor in the air expired from the nose or mouth or the odor of a tongue scraping, dental appliance, or length of dental floss. It is widely used in the evaluation of halitosis and is considered the gold standard despite its subjectivity . The quality of the odor can also be assessed (hedonic method), but this requires specific training, so it is infrequently done.
An oral or pharyngeal origin is suspected if the odor is largely confined to the mouth and not the nose (see 'Oral' above); nasal involvement is suspected if the odor emanates mainly from the nose (see 'Nasal' above). A systemic origin is suspected in the rare cases in which the odor emanates both from the mouth and nose and has the same quality. (See 'Systemic' above.)
A widely used scale uses the following scoring system :
●0 = no odor
●1 = barely detectable odor
●2 = slight odor
●3 = moderate odor
●4 = strong foul odor
●5 = unbearably strong foul odor
Mouth — Mouth odor is evaluated by asking the patient to breathe out though the mouth. The examiner smells the odor from a distance of 5 to 10 cm and scores the odor.
In addition, it may be helpful to ask the patient to count out loud to 20 and repeat the above. This is because the odor is sometimes more obvious when the patient is speaking.
Tongue — The tongue odor can be evaluated by taking a plastic spoon in one hand, a piece of gauze in the other, and asking the patient to stick out the tongue as far as possible and to hold his or her breath. Wrap the gauze around the tip of the tongue and hold it with one hand, using the spoon with the other hand to scoop up some of the mucus at the very back of the tongue dorsum towards the throat (about 12 cm from the tip of the adult tongue). Wait a few seconds. Smell and score the spoon. In many cases, a yellowish discharge is collected on the spoon; although there is no direct evidence, this discharge is probably postnasal drip. Excessive or viscous postnasal drip is extremely common and is usually not indicative of any frank nasal infection or other pathology .
Teeth — The contribution of the teeth to halitosis can be assessed by scoring the odor of dental floss after the patient has used it.
Dentures/dental restorations — If present, dentures and removable dental restorations should be removed and the odor scored.
Nose — Nasal odor is evaluated by asking the patient to close his or her mouth and breathe out through the nose. It is scored using the same scale as mouth odor.
Instrumental tests — Instrumental tests are objective tests that measure the level of VSCs. Such quantitative and semiquantitative measurements can be helpful, but they do not substitute for clinician judgment and should be used in conjunction with organoleptic tests. These tests are typically done by specialists in halitosis or in research settings.
Sulfide monitors — Measurements of mouth-air VSC content can be performed using portable sulfide monitors.
Subjects are asked to close their mouth for 120 to 180 seconds before mouth air is collected through a disposable plastic straw inserted deep into the oral cavity . A suction pump pulls the air into the instrument, where concentrations of VSCs are measured by an electrochemical sensor. The measurement takes only a few seconds and is expressed in ppb (parts per billion). Halitosis is usually defined by VSC concentrations >100 ppb [43,44].
Sulfide monitor readings are sensitive to reductions in oral odor levels following the use of mouth rinses, so these should not be used on the day of testing. While VSCs are the major cause of halitosis, it is important to recognize that non-VSC compounds are not detected by sulfide monitors and may contribute to halitosis. (See 'Pathogenesis' above.)
Gas chromatography — Portable gas chromatographic analyzers are also available to measure VSCs. They are equipped with an indium oxide semiconductor gas sensor which measures the concentration of hydrogen sulfide, methyl mercaptan, and dimethyl sulfide. Dimethyl sulfide is not well detected by sulfide monitors.
Samples are collected through a disposable plastic syringe inserted deep into the oral cavity and held between the lips. Subjects must close their mouth for 30 seconds before sample collection; 0.5 cc of air is then injected into the measuring device. The measurement of the concentrations of VSCs takes a few minutes and is expressed in ng/10 mL and ppb.
INDICATIONS FOR REFERRAL — The initial evaluation of patients complaining of bad breath can be done by the primary care clinician. However, referral to a specialist may be warranted in the following situations:
●Referral to a mental health provider is indicated for halitophobia (persistent distress about bad breath despite a negative evaluation). (See 'Subjective' above.)
●Referral to a neurologist is indicated if a neurologic basis for subjective halitosis is suspected (disorder of taste or smell present). (See 'Subjective' above.)
●Referral to a medical specialist is indicated if specialized diagnostic procedures (eg, endoscopy for evaluation of possible gastroesophageal origin of halitosis) are needed or if the underlying medical problem requires specialized care (eg, advanced liver or kidney disease). (See 'Systemic' above.)
●Referral to an otolaryngologist is indicated for patients with chronic caseous tonsillitis and tonsilloliths who have persistent halitosis despite conservative measure to improve oral hygiene (See "Tonsillectomy in adults: Indications", section on 'Halitosis'.)
Identifiable cause — Patients with an identifiable cause of bad breath should be treated for the condition.
●Gingivitis and periodontitis – Patients with gingivitis and periodontitis should be referred for appropriate treatment. (See "Overview of gingivitis and periodontitis in adults".)
●Dry mouth – If dry mouth can be attributed to a drug, that drug should be discontinued if possible. Otherwise, the dry mouth should be treated symptomatically. (See "Treatment of dry mouth and other non-ocular sicca symptoms in Sjögren’s disease", section on 'Treatment of dry mouth'.)
●Tonsillar pathology – Peritonsillar abscess should be treated appropriately. (See "Peritonsillar cellulitis and abscess", section on 'Management'.)
●Chronic caseous tonsillitis or tonsilloliths can generally be managed conservatively with self-cleaning of the tonsils. This includes gentle, directed self-irrigation of the tonsil to dislodge tonsilloliths as needed. Some specialists offer a laser CO2 cryptolysis procedure to prevent stone formation, but this procedure has not been widely adopted as there are few data supporting its long-term efficacy [45-47]. If severe halitosis and symptomatic tonsilloliths persist despite conservative measures, tonsillectomy can be considered in select patients. (See "Tonsillectomy in adults: Indications", section on 'Halitosis'.)
●Acute or chronic sinusitis should be treated appropriately. (See "Uncomplicated acute sinusitis and rhinosinusitis in adults: Treatment" and "Chronic rhinosinusitis: Clinical manifestations, pathophysiology, and diagnosis".)
●Postnasal drip should be treated appropriately. (See "Chronic nonallergic rhinitis" and "Pharmacotherapy of allergic rhinitis" and "Subcutaneous immunotherapy (SCIT) for allergic rhinoconjunctivitis and asthma: Indications and efficacy".)
No cause identified — For patients with halitosis without an identifiable cause, a variety of self-care measures (including lifestyle modifications) can be employed. Although there is a lack of high-quality evidence demonstrating the efficacy of most of these interventions , they are worth attempting as many patients may experience symptomatic improvement. Such interventions include:
●Sugar-free chewing gums (which stimulate saliva production).
●Decreasing alcohol and coffee intake.
●Proper dental care and oral hygiene, including daily flossing.
●Gentle cleaning of the posterior portion of the tongue dorsum (eg, with a plastic tongue cleaner).
●Rinsing and gargling with a mouthwash before bedtime.
The best time to use a mouthwash is probably before bedtime, since the residue of the mouthrinse may remain in the mouth for a longer period of time and have a greater effect. In addition, bacterial activity leading to bad breath is greatest during sleep, when saliva flow is practically zero and microbial activity is highest. The quaternary agents active in many mouthwashes (cetylpyridinium chloride, chlorhexidine) may be inactivated by the anionic detergents in toothpastes; thus, patients should be advised to use mouthrinse an hour or more after brushing their teeth. Since much of the odor is associated with the posterior dorsal tongue, it is important to gargle in addition to oral rinsing.
The most efficacious oral rinses for short-term use are those containing chlorhexidine gluconate 0.2%, but in the United States only 0.12% is readily available . Common side effects from chlorhexidine rinses are temporary teeth staining and taste disturbances. Tooth discoloration resolves completely with a professional dental cleaning.
Subjective halitosis — Patients with subjective psychologic halitosis generally respond to reassurance. If significant concern persists despite reassurance, then referral to a mental health provider is indicated to assess for halitophobia.
If subjective halitosis from a neurologic cause is suspected because of the presence of dysgeusia or dysosmia, a referral to a neurologist is indicated.
SUMMARY AND RECOMMENDATIONS
●Halitosis or bad breath is a common condition. Patients may not be aware of their own bad breath and learn of it from another person. (See 'Epidemiology' above.)
●Physiologic halitosis is bad breath that does not have a specific pathologic cause. It is worse upon awakening and results from the action of bacteria on the dorsum of the tongue on desquamated epithelial cells and entrapped food particles. (See 'Physiologic' above.)
●The evaluation of bad breath includes a history and physical examination that is targeted toward finding a treatable cause of halitosis, and can be supplemented with organoleptic and/or instrumental tests to measure the volatile sulfur components. (See 'Evaluation' above.)
●Although the evaluation of patients complaining of bad breath can be done by the primary care clinician, referral to a dentist, mental health provider, or medical specialist may be warranted if certain conditions are identified or suspected (eg, gingivitis or periodontitis, halitophobia, neurologic disorder). (See 'Indications for referral' above.)
●If no specific cause can be found for the halitosis, many patients will improve with measures to improve dental and oral hygiene, including regular tooth brushing, daily flossing, gentle cleaning of the tongue dorsum with a plastic tongue cleaner, and use of a mouthwash before bedtime. (See 'Management' above.)
ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge Mel Rosenberg, PhD, who contributed to an earlier version of this topic review.
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