Halitosis: what causes bad breath and how is it treated?

Halitosis, also known as bad breath, can be temporary or persistent. In approximately 80–90% of cases, the cause originates in the oral cavity, most commonly on the tongue, around the gums or in areas where bacterial plaque accumulates. If bad breath persists despite proper oral hygiene, the cause should be identified before choosing the appropriate treatment.

Halitosis at a glance

• halitosis means persistent bad breath;
• 80–90% of cases have an oral cause;
• bacterial deposits on the tongue and periodontal disease are important causes;
• dry mouth, smoking and certain foods can contribute;
• a smaller proportion of cases have ENT, digestive or systemic causes;
• effective treatment depends on identifying the cause.

Halitosis describes an unpleasant odour in exhaled air. However, not every change in breath indicates a medical condition. Bad breath may occur temporarily after eating certain foods or may persist because of an oral problem or, less commonly, a condition outside the oral cavity.

It can be difficult to assess your own breath objectively. Some people may be unaware of the odour, while others may perceive it even when it is not noticed by those around them. When halitosis is suspected, a dental examination can help identify its source.

Temporary bad breath

Breath may have an unpleasant odour in the morning, after long periods without food or fluids, or following the consumption of garlic, onions, spices, coffee or alcohol.

Saliva production decreases during sleep. As a result, bacteria and food debris are removed more slowly, allowing unpleasant-smelling compounds to accumulate. Morning breath usually improves after drinking water, brushing the teeth and cleaning the tongue.

Persistent halitosis

Halitosis becomes a problem when the odour persists or returns frequently and cannot be explained by diet alone. In these situations, chewing gum, oral sprays and mints may temporarily mask the odour, but they do not treat its cause.

Persistent halitosis may be associated with bacterial deposits on the tongue, gingivitis, periodontitis, tooth decay, dental infections or reduced saliva production. Identifying the source is essential for choosing the appropriate treatment.

The characteristic odour mainly occurs when bacteria break down food debris, shed cells and proteins in the oral cavity. This process releases volatile sulphur compounds, which are responsible for many cases of oral halitosis.

Plaque or tartar

Deposits of plaque or tartar can cause bad breath, especially if there are retention areas, such as dental crowding or narrow spaces created by braces. Learn more about halitosis caused by braces.

Regular prophylaxis sessions that include scaling and Airflow are effective in removing plaque and tartar.

Bacterial deposits on the tongue

The surface of the tongue has numerous grooves and papillae where bacteria, food debris and shed cells can accumulate. Tongue coating, particularly at the back of the tongue, is one of the main sources of bad breath.

Cleaning the tongue can reduce these deposits, but it should be done gently to avoid irritation, injury or bleeding.

Gingivitis and periodontitis

Bacterial plaque and tartar accumulated on the teeth and beneath the gums can cause gingival inflammation. Regular professional dental prophylaxis helps remove these deposits and maintain gum health.

Periodontitis can cause spaces known as periodontal pockets to form between the teeth and gums. Bacteria inside these pockets are difficult to remove through regular oral hygiene. These deposits may contribute to persistent halitosis and can be accompanied by gum recession, tooth mobility or bone loss.

Tooth decay and oral infections

Deep cavities, food debris retained inside them, dental infections and untreated dental abscesses may produce an unpleasant odour. Halitosis can also be associated with dental restorations that no longer fit properly or with dentures that are not cleaned adequately.

Treatment is determined following a clinical examination and, when necessary, diagnostic imaging.

Xerostomia

Xerostomia refers to the sensation of dry mouth and may be associated with reduced saliva production. Saliva helps clean the oral cavity and neutralise the acids produced by bacteria. When saliva flow decreases, bacterial plaque and food debris can accumulate more easily.

Dry mouth may be caused by dehydration, mouth breathing, smoking, certain medications or conditions affecting the salivary glands. If the symptom persists, its cause should be investigated.

Smoking

Tobacco leaves a distinctive odour in the mouth and can contribute to dry mouth. Smoking also increases the risk of gum and periodontal disease, which can cause or worsen halitosis.

Smoking may alter the sense of smell as well, which means that some smokers may not notice their own bad breath.

Food and drinks

Garlic, onions, certain spices, coffee and alcohol can temporarily change the smell of the breath. After digestion, some substances enter the bloodstream and are eliminated through the lungs. For this reason, brushing may reduce odours inside the mouth but may not eliminate them immediately.

Very restrictive diets and long periods of fasting may also change the smell of the breath.

Yes, although extraoral causes are less common than problems originating in the oral cavity. If the dentist rules out a dental or periodontal cause, they may recommend an assessment by another medical specialist.

Possible extraoral causes include:

• sinus infections and postnasal drip;
• tonsillitis and deposits that form in the tonsils;
• mouth breathing and nasal obstruction;
• gastro-oesophageal reflux in certain cases;
• some respiratory conditions;
• uncontrolled diabetes;
• advanced kidney or liver disease;
• medications that reduce saliva production.

Digestive conditions are not the main cause of halitosis. For this reason, the assessment usually begins with a dental examination. Additional investigations may then be recommended depending on the symptoms and examination results.

Treatment depends on the underlying cause. Products that freshen the breath may have a temporary effect, but halitosis will return if its source is not addressed.

Treating dental and periodontal causes

If halitosis is associated with bacterial plaque, tartar, gingivitis or periodontitis, treatment may include professional dental cleaning, removal of deposits from beneath the gumline and periodontal treatment.

Tooth decay, dental infections and poorly fitting restorations or prosthetic work must be treated separately. The dentist will determine the appropriate course of treatment after examining the entire oral cavity.

Tongue cleaning and oral hygiene

Daily oral hygiene should include:

• brushing the teeth twice a day for approximately two minutes;
• using fluoride toothpaste;
• cleaning between the teeth every day with dental floss or interdental brushes;
• gently cleaning the tongue with a tongue scraper or dedicated cleaning device;
• cleaning dentures or removable dental appliances every day.

An oral irrigator may complement oral hygiene in certain situations, but it does not replace brushing or the mechanical cleaning of the spaces between the teeth.

Managing dry mouth

Regular hydration and stimulating saliva production may help when halitosis is associated with dry mouth. Sugar-free chewing gum can temporarily stimulate saliva flow when there are no contraindications.

If xerostomia persists, the doctor or dentist can assess its possible causes, including the medication being taken. Prescribed treatment should not be stopped or changed without the recommendation of the prescribing doctor.

The role of breath-freshening products

Mouthwash, oral sprays and mints may temporarily reduce the odour, but they do not replace dental treatment. Some mouthwashes contain antibacterial ingredients, although the appropriate product and duration of use should be selected according to the patient’s needs.

Products containing alcohol may worsen dry mouth in some people. Long-term use of medicated mouthwash without professional advice is not recommended.

Treating extraoral causes

When the dental examination does not identify an oral cause, the patient may be referred to their general practitioner or to an ENT specialist, gastroenterologist or another appropriate medical specialist.

Treatment will target the condition responsible for the symptom. Halitosis is not treated separately when its source is outside the oral cavity.

To reduce the risk of bad breath returning:

• brush your teeth twice a day;
• clean between your teeth and clean your tongue every day;
• attend regular dental check-ups and professional cleaning appointments;
• drink enough water;
• avoid smoking;
• limit excessive alcohol consumption;
• clean dentures and removable dental appliances properly;
• avoid masking persistent odours with mints or other breath-freshening products;
• request an assessment if you experience bleeding gums, dental pain or persistent dry mouth.

The recommended frequency of dental check-ups and professional cleaning appointments is established individually according to gum health, the risk of tooth decay and existing dental treatments.

Schedule a dental consultation if bad breath persists for several weeks despite following an appropriate oral hygiene routine.

A dental assessment is also recommended if halitosis is accompanied by:

• red, swollen or bleeding gums;
• visible tartar deposits;
• a persistent unpleasant taste;
• toothache;
• sensitivity or swelling around the gums;
• discharge around a tooth;
• loose teeth;
• persistent dry mouth;
• problems with dentures or dental restorations.

The dentist can examine the teeth, gums, tongue and dental work to identify the source. If no oral cause is found, further medical investigations may be recommended.

Persistent bad breath may be a sign of a problem that requires treatment.