How do I get rid of my bad breath?

What causes bad breath

Halitosis is caused predominantly by sulphur-producing bacteria that normally live on the surface of the tongue and in the throat.

Sometimes those bacteria start breaking down proteins at a very high rate, releasing odorous volatile sulphur compounds — principally hydrogen sulphide, methyl mercaptan and dimethyl sulphide.

That is the mechanism, and it explains why the tongue — not the teeth — is usually where the problem sits.

Most persistent bad breath starts in the mouth. Quirynen and colleagues examined 2,000 consecutive patients at a multidisciplinary bad-breath clinic in Leuven, Belgium, and reported in the Journal of Clinical Periodontology in 2009 that "for 76% of the patients, an oral cause was found" — tongue coating in 43 per cent, gingivitis or periodontitis in 11 per cent, and a combination of the two in 18 per cent. Sixteen per cent had pseudo-halitosis or halitophobia, meaning no odour could be objectively detected at all, and 4 per cent had an ear, nose and throat or other non-oral cause.

The figure quoted almost everywhere else is "85 to 90 per cent" — the same Leuven data recalculated to count only those in whom malodour was objectively confirmed. Either way, these were self-selected attenders at a specialist clinic, not a general population. The common misconception is that bad breath comes from the stomach. In that series it very rarely did. What causes bad breath and how can I fix it? covers the same ground from the diagnosis end, and bad breath is the service page.

Prevalence figures disagree wildly. The one pooled estimate, Silva and colleagues in Clinical Oral Investigations in 2018, combined 13 population-based studies and reported 31.8 per cent (95% CI 24.6–39.0%), with high heterogeneity between them. Other published figures range from about 2.4 per cent to more than half the population. Treat any single percentage with caution.

Common causes

Beyond the bacteria colonising the back of the tongue:

Dental factors — infection (periodontitis), or poor oral hygiene. What is gum disease? covers the reversible early stage; periodontal (gum) disease covers what lies past it
Dry mouth — often from medication, alcohol, stress, or an existing medical condition. My mouth is always dry — why is this and does it affect my teeth? and my mouth always feels dry! What can I do?
Smoking — and vaping, which produces the same dry-mouth effect
Acid reflux from the stomach — see what is dental erosion and how is it addressed? for what reflux does to the teeth themselves
Post-nasal discharge — and habitual mouth breathing, covered in mouth breathing: the silent habit
Medical conditions — kidney failure, metabolic dysfunction, biochemical disorders. Diabetes and oral health is the most common one to check
Certain foods — onions, garlic, cauliflower — though their effects are short-lived

That last distinction matters. Food-related breath resolves by itself; the other six do not.

A note on food: garlic, onion and alcohol are absorbed into the bloodstream and exhaled from the lungs. No amount of brushing or rinsing reaches that. It has to be metabolised, which takes hours.

Two more oral sources worth knowing, because they are commonly missed:

Tonsil stones (tonsilloliths) — small calcified plugs in the tonsillar crypts. Genuinely malodorous, entirely harmless, and often invisible to the person who has them.
Dentures, particularly if worn overnight or not cleaned daily — five things you should know about your new dentures, caring for yourself and your immediate dentures, and dentures.

The Australian Dental Association's consumer site adds the one most often missed: bad breath "can actually be caused by other areas of the body including the lungs and the nose". A mouth that examines clean is a reason to look further, not a reason to try another product.

Symptoms

A white coating on the tongue, especially at the back
Dry mouth
Build-up around the teeth
Post-nasal drip or mucous
Particularly bad morning breath
Thick saliva and a constant need to clear your throat
A constant sour, bitter or metallic taste

The combination you notice narrows the cause considerably: a white coating at the back of the tongue points one way; thick saliva and throat-clearing point to post-nasal drip; a metallic taste with dry mouth points to medication or a systemic cause.

Morning breath on its own is normal and is not halitosis. Salivary flow falls during sleep in everybody, so the bacteria are unopposed for eight hours. It resolves with breakfast and brushing. It is only a sign of something when it persists through the day. On the order of breakfast and brushing, brushing your teeth: before or after breakfast? is the relevant argument.

The symptoms that are not about breath at all

Bad breath is a nuisance. These are not, and they are not an appointment — they are a hospital emergency department, or 000:

Facial swelling that is spreading, particularly toward the eye or down into the neck or under the jaw
Difficulty breathing or swallowing, or a change in your voice
Fever together with dental pain
Bleeding from the mouth that will not stop

A foul taste or smell with a swollen, painful area usually means a dental abscess, and an abscess that is spreading is treated as urgent — why are dental abscesses so painful?, what is a tooth abscess? Should I have it treated?, and can a dental abscess affect your general health?. For urgent problems that are not in the list above, emergency dentistry explains what can be seen on the day.

The awkward part: you cannot smell your own breath

This is a real physiological effect — you adapt to your own odour and stop perceiving it. Cupping a hand over your mouth and breathing into it does not work, because you are still smelling air you are already adapted to.

It is also measurable. In a population-based study of 419 residents of Bern, Switzerland, 32 per cent reported sometimes or often having bad breath, while 11.5 per cent met the objective threshold on examination — and Bornstein and colleagues concluded that "only a weak correlation between self-reported halitosis and either organoleptic or VSC measurements could be detected". It cuts both ways: some people who worry are fine, and some people who are not worried do have it.

Slightly better home tests: lick the inside of your wrist, let it dry for ten seconds and smell it; or draw floss between your back teeth and smell the floss. Neither is reliable.

Ask someone you trust. It is a genuinely kind thing to be told, and it is the only accurate method available at home.

Treatment

There is no single treatment for halitosis. What works depends on what is causing it — which is why guessing at products rarely resolves it. Nobody can promise you permanently fresh breath; how can I guarantee I always have fresh breath? takes that question apart directly.

That is not just caution. The 2019 Cochrane review Interventions for managing halitosis pooled 44 trials and 1,809 participants and concluded: "We were unable to draw any conclusions regarding the superiority of any intervention or concentration." Only one of its comparisons reached even low-certainty evidence. So the order of business is to find the cause, not to buy a solution.

The foundation

Good oral hygiene, including brushing and flossing twice a day, is crucial. What is the ideal daily routine for oral hygiene? sets out the whole routine, and is flossing really that important? answers the part most people skip.

A tongue brush or tongue scraper is commonly recommended — and here the evidence is genuinely weak. The Australian Dental Association's consumer site states that "a review of the scientific evidence in 2019 found no evidence that cleaning your tongue, using several different methods including mouthwash or chewing gum, were effective for managing the cause of halitosis". The Cochrane review it refers to put mechanical tongue cleaning ahead of no tongue cleaning on the dentist-assessed odour score by a mean difference of −0.20 (95% CI −0.34 to −0.07), from 2 trials and 46 participants, rated very low-certainty evidence. The ADA's own summary box is more positive than the body of the same page; its page description resolves the two by saying tongue cleaning reduces the bacterial load "but the impact of this reduction has not been proven yet". Clean your tongue if you find it helps, and do not expect it to be the answer on its own.

The steps that make up sensible management:

Clean the back of the tongue, daily, gently. The ADA's instruction is to "start gently at the back of the tongue, pulling or brushing forward and use water to lubricate the process so the brush doesn't drag along the tongue surface", and it warns that "you need to be very gentle because the tongue surface is delicate and sensitive". A soft toothbrush is acceptable; a scraper is also fine. The 2014 international consensus workshop on halitosis adds two restrictions: the top surface only, not the sides, and no case for tongue cleaning where there is no coating. Which toothbrushes do dentists recommend? and how to care for your toothbrush cover the equipment.
Clean between the teeth, daily. Interdental brushes where the gaps admit them; floss where they do not.
Have gum disease treated. If pockets are deep, no home care will resolve the smell — healthy pockets measure 4mm or less; 5mm or more indicates periodontitis. When do you need deeper cleaning? explains scaling and root planing, bleeding gums covers the commonest first sign, and periodontists are the specialists who manage the advanced cases.
Address dry mouth — water, sugar-free gum to stimulate flow, saliva substitutes, and reviewing medications with the prescriber. Do not stop any medication over this. Does chewing sugar-free gum really help prevent cavities? explains why the gum works, and what causes dry mouth during running? covers the exercise version.
Treat untreated decay and failing restorations — why do I need a filling? and how long do dental fillings last?
Stop smoking. Quitline is 13 7848.

For specific causes

Chronic sinusitis — a saline nasal spray may help.

Bacterial overgrowth — a course of antibiotics effective against anaerobic bacteria may be used to reduce the overgrowth of sulphur-producing bacteria. That is a prescription decision made by a clinician after diagnosis, not a self-treatment, and antibiotics are not a general answer to halitosis.

What does not work

Mouthwash. It masks for twenty minutes to an hour and treats nothing. Alcohol-based rinses dry the mouth and can make matters worse over time. Antibacterial rinses do reduce the bacterial load, but the evidence that this reaches the breath is thin. In the Cochrane review, a mouthwash containing chlorhexidine and zinc acetate against a placebo gave a mean difference of −0.20 (95% CI −0.58 to 0.18) — a range that includes no benefit at all. The only comparison to reach low-certainty evidence was brushing plus a cetylpyridinium chloride mouthwash against brushing alone (−0.48, 95% CI −0.72 to −0.24, 1 trial, 70 participants) — an adjunct to brushing, not a replacement. Chlorhexidine also stains teeth and alters taste with prolonged use, so it is a short course prescribed for a reason, not a daily habit. The truth and myths about mouthwashes and should I be using mouthwash as well as brushing and flossing my teeth? go further into this.

Sugared mints and chewing gum. They mask the smell, feed the bacteria and cause decay. Sugar-free gum is genuinely useful — not for the flavour, but because it stimulates saliva. How does sugar affect your dental health?

Treating your stomach. Almost never the cause.

Charcoal products. No evidence for halitosis, and they abrade enamel — home whitening and charcoal whitening: does it work? Is it safe?

Oil pulling. No good evidence, and it delays actual diagnosis — can oil pulling make my mouth healthier and my teeth whiter?

And the opposite problem, which is also real

Halitophobia — a persistent conviction of having bad breath when no odour is detectable to others and no cause is found on examination. It is recognised, it is genuinely distressing, and it does not respond to more mouthwash.

It is also not rare. In the Leuven series, pseudo-halitosis or halitophobia was diagnosed in 16 per cent — four times the rate of ear, nose and throat or other non-oral causes in the same group. A careful examination that finds nothing is a real result, not a dead end.

Where examination and objective assessment find nothing, the useful next step is a conversation with a GP, not another product.

What to do next

Speak to your dentist or hygienist to work out the most effective treatment for you. Dental cleans and hygienists, what does a dental hygienist do?, and your Smile Solutions hygienist visit: what to expect.

If oral causes are excluded and the problem persists, the next step is your GP — several of the causes listed above are medical rather than dental.

See a dentist sooner if the bad breath comes with bleeding gums — that combination is gum disease until proven otherwise. See a GP sooner if there is a distinctive sweet, acetone-like or ammonia-like odour, or any general symptoms alongside it.

And the standing rule: any ulcer, white patch, red patch or lump that has not healed in three weeks needs examining. The cause of mouth ulcers and their usual treatments and oral cancer: how your dentist can help with early detection explain why that rule exists.

Common questions

Should I brush and rinse thoroughly before the appointment?

No — and this is the single most counter-productive thing people do, because it hides the very thing you are asking to have assessed.

The 2014 international consensus workshop on halitosis management, published in the Journal of Breath Research, sets out what a patient should be asked to do before a first breath assessment. The assessment should be done in the morning, and before it the patient is instructed to avoid:

any fragrance or masking product
smoking
anything in the mouth except water on the morning of the examination — no food, no drink
tongue cleaning for 24 hours beforehand
antibiotic treatment for at least three weeks, and preferably six to eight weeks, before the examination

That last one is not something to act on by yourself. It means that if you have recently finished a course of antibiotics for any reason, say so when you book, because it may be worth waiting.

How is bad breath actually measured? Is it just somebody's opinion?

Partly, and deliberately so. The same consensus workshop states that "the organoleptic measurement is mandatory, even if an instrumental detection is performed" — a trained assessor smelling the breath remains the reference standard, because the human nose responds to odours no single-gas sensor reads. The workshop found that a panel of judges does not improve accuracy over one judge.

The odour is scored on a defined scale rather than described loosely. The commonly used six-point scale runs from 0, no appreciable odour, through 2, slight but clearly noticeable, 3, moderate, to 5, severe. A simpler alternative grades by the distance at which it is detectable — about 10 cm, about 30 cm, about 100 cm. For scale, in the Leuven series of 2,000 clinic attenders most scored below 3.

The part that actually locates the problem is a comparison: "an organoleptic test at the first appointment should always be performed on oral and nasal air. By comparing the mouth and the nose exhaled air intra-oral halitosis can be distinguished from nasal and blood-borne extra-oral halitosis." Healthdirect describes the same test in plain terms — your dentist may compare your mouth breathing with your nose breathing. If the odour is in the nasal air, the mouth is not the source, and more dental treatment will not fix it.

Instruments exist — the workshop names the Halimeter and the OralChroma — but they are adjuncts, they need regular calibration, and a single OralChroma measurement takes eight minutes. Not every practice has one, and their absence does not prevent a proper assessment.

I cough up small, hard, white lumps. Is that what I am smelling?

Quite possibly. Those are tonsilloliths — tonsil stones — and they genuinely smell, because the bacteria found in them are the same anaerobic groups that produce volatile sulphur compounds.

Bollen and Beikler's review in the International Journal of Oral Science reports that "the presence of tonsilloliths represents a 10-fold increased risk of abnormal VSC levels" (a figure that traces to a 1988 paper, so treat it as indicative rather than precise). Their wider point is the useful one: "maximally 10% of the oral malodour cases originate from the ears, nose and throat region, from which 3% finds its origin at the tonsils" — and they advise that when the mouth is examined, "attention should first be paid to the tonsils".

The reassurance is that they are harmless. The same review is blunt about the surgical question: "tonsilloliths are asymptomatic phenomena and are therefore never a reason for tonsillectomy", and a tonsillectomy for breath is considered only when oral hygiene measures have not improved it. Repeated acute tonsillitis — more than three episodes a year — is a separate conversation, and it belongs to an ear, nose and throat doctor rather than to a dentist.

My mouth has been checked and it is clean. What medical causes should my GP consider?

The ones documented in the literature each have a characteristic odour, which is why describing the smell to your doctor is more useful than describing it as simply "bad".

Bollen and Beikler list renal failure, cirrhosis of the liver and diabetes mellitus among the well-documented non-oral causes. Chronic renal failure produces "a typical uremic odour in combination with a dry mouth"; diabetic ketoacidosis leads to a typical breath odour, and type 2 diabetes is described as giving a "sweet and fruity" one. A distinctly fishy odour can indicate trimethylaminuria, an inherited enzyme deficiency the same authors call the largest cause of undiagnosed body odour; it is diagnosed by measuring trimethylamine in urine, not by anything done in a dental chair.

On the stomach — the explanation most people arrive with — the same review is specific: the gastrointestinal tract can only influence breath indirectly, and the belief that halitosis originates in the stomach "is only correct in <0.5% of the cases". Severe regurgitation and chronic sinusitis are the more realistic non-oral candidates; in chronic sinusitis the authors report that 50 to 70 per cent of patients complain of oral malodour.

Medicines matter mainly through dry mouth rather than through any smell of their own. That is worth raising with whoever prescribed them, at a review — not a reason to stop or change anything on your own.

I have had this for years and never raised it. Is that unusual?

It is the norm, unfortunately. In the Leuven series, patients attending that clinic had been living with the complaint for a mean of seven years (standard deviation eight years), and most arrived without a referral — they had found the clinic themselves rather than being sent.

Nor is the problem rare enough to be embarrassing. The one pooled prevalence estimate, from 13 population-based studies, puts it at 31.8 per cent of adolescents and adults (95% CI 24.6–39.0%), with the authors noting high variation between studies and a worldwide trend upward.

The practical consequence of waiting is not that the condition becomes untreatable — it is that gum disease, decay or a dry mouth that might have been simple at the start has had years to progress. Raising it at a routine check-up costs you one sentence, and it is an entirely ordinary thing for a dental team to be asked about.

Practical details

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Every practitioner's registration can be verified free on the AHPRA public register at ahpra.gov.au. The practice's registered specialists are identified as such within the full team.

Published 5 July 2016. General information only — it is not a diagnosis or a treatment plan, and it does not replace advice from your treating practitioner or doctor. No medication should be started or stopped on the basis of this page.

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