A breath of fresh air – an overview of halitosis

Richard Horwitz and Bradley Lander present an overview of halitosis for the dental professional.

Bad breath, otherwise known as halitosis or oral malodour, is a common problem that can affect anyone at any age. Halitosis originates from oral or non-oral sources and can be defined as an unpleasant or offensive odour from the mouth.

Notwithstanding its social and personal implications, it is no surprise that halitosis is one of the most frequent complaints from patients to their dentist (Loesche and Kazor, 2002).

Halitosis is something that is personal to each of our patients and often ignored through embarrassment. Therefore, the aim of this article is to improve readers’ awareness of the aetiology, assessment and management of halitosis in the general dental practice.

While not often talked about, halitosis is ubiquitous amongst our patients. A systematic review and meta-regression analysis by Silva and co-workers (2018) suggested a worldwide trend towards a rise in halitosis prevalence. Although prevalence studies in the United Kingdom are limited, Rösing & Loesche (2011) provide a summary of descriptive epidemiological studies concerning halitosis is outlined in Table 1.

Table 1: A summary of descriptive epidemiological studies concerning halitosis (adapted from Rösing & Loesche, 2011)


Several studies suggest an oral cause of halitosis in as many as 85% of patients presenting with malodour (Eldarrat, 2011), most commonly with a bacterial origin (Allaker, 2010).

The main microorganisms associated with halitosis are listed in Table 2 and are known to degrade sulphur-containing substrates on the surfaces of the oral cavity. These volatile sulphur compounds (VSCs) are mainly produced by gram-negative bacteria that are also responsible for periodontal disease, thus a positive correlation exists between bad breath and periodontitis (Bollen and Beikler, 2012). Consequently, the bacterial composition of subgingival plaque appears to be identical to that of the dorsal surface of the tongue (Greenman et al, 2004).

Tongue coating

Roldán and co-workers (2003) claimed that a tongue coating is one of the most common causes for oral malodour. With a relatively large surface area, and acting as a nutritional reservoir, the dorsal surface of the tongue provides the ideal environment for halitosis-causing bacteria to thrive.

Morning breath

Anaerobic putrefaction will increase while sleeping due to a reduced saliva production during the night. As this is a non-pathological cause of halitosis, improving oral hygiene should reduce oral malodour experienced when waking (Suarez et al, 2000).

Odontogenic halitosis

As discussed, the link between periodontal diseases and halitosis is well-established. Yaegaki and Sanada (1992) proved a positive correlation between the depth of periodontal pockets and the concentration of sulphur components. Additionally, poor oral hygiene, dental plaque, dental caries and poorly cleaned dentures can also be linked to halitosis (Bollen and Beikler, 2012).

Other odontogenic causes of halitosis include exposed tooth pulps, extraction wounds, peri-implantitis and pericoronitis. Therefore, it is imperative to stabilise any active disease and improve overall self-dental maintenance in order to rule out odontogenic halitosis as a cause.


Patients with a dry mouth are susceptible to experiencing halitosis due to an associated increase in dental plaque (Albuquerque et al, 2010).

Additionally, a reduction in the anti-microbial effects of saliva in xerostomia further facilitates habituation of halitosis-causing organisms (Almståhl and Wikström, 1999).

Ears, nose and throat

Van den Broek and co-workers (2007) estimated that the ears, nose and throat (ENT) region contributed to, at most, 10% of all oral malodours.

Tonsillitis of bacterial origin and tonsilloliths result in abnormal VSC levels and therefore has the potential to cause halitosis. Consequently, significant attention should be paid to the tonsils during clinical investigation.

Other causes of halitosis from the ENT region include sinusitis and a postnasal drip.


Less than 0.5% of halitosis originates from the stomach (Bollen and Beikler, 2012).

Zenker’s diverticulum, stomach infections with helicobacter pylori and intestinal obstruction have been hypothesised to result in oral malodour, however, further research is required in order to identify a strong correlation between these occurrences and halitosis.

Hepatology and endocrinology

Table 2: Microorganisms relating to halitosis (Adapted from Greenman et al, 2004)

Fetor hepaticus (known as ‘the breath of the dead’) is a recognised condition that occurs as a result of reduced liver function. Patients may report their breath to be sweet, musty and faecal in nature. Fetor hepaticus occurs when waste products are eliminated through the lungs, causing unpleasant odours.

Tyrosinemia is a hereditary condition whereby tyrosine is not broken down completely. As a result, the amino acid and its by-products build up in tissues that can cause a cabbage-like malodour. 

Metabolic and endocrinological factors also contribute to oral malodour. This includes diabetes, alcoholic keto-acidosis, kidney insufficiency, trimethylaminuria, phenylketonuria, homocystinuria and Disease of Lignac (Bollen and Beikler, 2012).


Xerostomia is a common side effect of many medications, including but not exclusive to:

  • Antihistamines
  • Sedatives
  • Amphetamines
  • Antidepressants
  • Diuretics
  • Decongestants
  • Anticholinergics
  • Antipsychotics.

Other medications may have an indirect influence on halitosis. For example, medication-related osteonecrosis of the jaw often presents with severe halitosis.


Halitophobia describes a psychological condition where patients are convinced of bad breath when there is none. Patients become paranoid and become fixated with cleaning teeth, chewing gum and using mouth fresheners. Treatments include cognitive behavioural therapy and helping patients overcome paranoia (Matsuoka et al, 2017).

Investigating halitosis

Some centres are able to objectively measure VSCs using a portable sulphide monitor known as a Halimeter (Interscan Corp) (Figure 1), however this is unable to differentiate between the various sulphides and cannot detect other classes of volatile compounds.

Gas chromatography analysis can detect different air compounds, including VSCs, with high sensitivity and specificity and can be performed on breath, saliva and tongue debris. However, this technique requires well-trained staff and is expensive.

Assessment is thus generally based upon organoleptic assessment of exhaled air, namely completed by the clinician. Such assessment requires an assessor smelling the air exhaled from the mouth and nose in order to subjectively confirm or deny the presence of malodour (Donaldson et al, 2007).

The intensity of breath odour is often rated as follows (Rosenberg, 1996):

  • Odour cannot be detected
  • Questionable malodour; barely detectable
  • Slight malodour, exceeds the threshold of malodour recognition
  • Malodour is definitely detected
  • Strong malodour
  • Very strong malodour.

Smelling both nose and mouth air is important. Malodour detectable from the nose alone (asking the patient to breath while their mouth is closed) is most likely to originate from nose, sinuses, elsewhere in the respiratory tract or from the gastrointestinal tract.

For optimal results, it is recommended that the patient should refrain from spicy foods, garlic or onions for at least 24 hours prior to the examination. Strong odours such as perfumes and smoking will influence organoleptic scoring and are therefore best avoided prior to an exam.

Despite its subjectivity and questionable reproducibility, organoleptic scoring is still considered to be the gold standard in the assessing halitosis.

Treatments and prevention of halitosis

Table 3: The types of halitosis

As the causes of halitosis are related to bacteria, therapies tend to have two main aims: either bactericidal, or to mask the volatile odoriferous compounds. This may be achieved through a combined approached of mechanical and chemical reduction.

Mechanical reduction of intraoral nutrients and microorganisms is fundamental. Oral hygiene practices need to cover effective removal of marginal plaque with good toothbrushing, interproximal spaces with interdental brushes and cleaning of the tongue.

Tongue cleaning is by no means a modern phenomenon and traces back to ancient civilisations. The tongue dorsum has many folds, furrows and crypts from the papillae present provide a vast surface area for microorganisms to colonise. Modern tongue-scraping instruments can include a ‘horse-shoe’ shape plastic ribbon or use of a toothbrush.

Despite limited research comparing these methods of tongue cleaning, there is a small but statistically significant finding that toothbrushing is less effective than tongue scrapers (Outhouse et al, 2006). Notwithstanding the overall aim of reducing tongue coating, there is strong evidence to support tongue brushing or scraping in succeeding to reduce halitosis and improve taste (Van der Sleen et al, 2010).

Amongst the many chemical agents available, commonly occurring ingredients include essential oil mouth rinses (Eli et al, 1996), triclosan with zinc or co-polymer (Hu et al, 2005) and chlorhexidine (Roldán, Herrera and Sanz, 2003). These agents work by reducing either plaque levels or result in a reduction of VSCs.

In order for chemical reduction to be effective, chemical agents must be used in conjunction with good oral hygiene practice.

Agents that are able to mask halitosis include rinsing products, sprays, mint tablets or chewing gum. They largely work by increasing saliva flow.

Where non-oral causes of halitosis are suspected, it would be sensible to liaise with the patient’s GP in order to further investigate a systemic cause and assess whether referral to a specialist is appropriate.

In cases of halitophobia, it may be necessary to refer the patient to a psychologist or psychiatrist for psychological counselling.

Some patients, however, may become convinced of their cure following conventional therapy despite never having a true halitosis. This phenomenon is known as pseudo-halitosis. Patients suffering from the condition have been shown to express symptoms of depression (Suzuki et al, 2008).

Figure 1: Halimeter (Interscan Corp)


Patients suffering from halitosis often experience psychological consequences. This can lead to social and professional anxieties, including feelings of low self-esteem, self-deprecation. Also, behavioural changes such as talking less or avoiding talking to people in close contact (Eli et al, 1996). Therefore, assessment and discussion of halitosis requires a large degree of sensitivity in order to avoid compromising the patient-dentist relationship.

As dental professionals, when managing patients with halitosis, consider the following:

  • Ask patients whether they have noticed an altered or bad breath
  • Find out whether the patient notices any associated factors (time of day, influence of particular foods/drinks, time of first onset)
  • Take a thorough dental history, including their home oral hygiene regime
  • Assess the severity of halitosis using a recognised rating system (Rosenberg, 1996)
  • Discuss local measures – reinforce good oral hygiene practices and masking agents (ie mouthrinses)
  • Be aware of the psychological impact of a true halitosis and pseudo-halitosis
  • Referral to patient’s physician if systemic cause suspected.

While there is a considerable body of research in this field, further research is required in order to identify practical approaches to assessment, diagnosis and management.

This article first appeared in Clinical Dentistry magazine. For more articles like this, you can sign up here.

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