Bad breath (halitosis) is an unpleasant odor on the breath that can be noticed by others. A short-lived odor on waking in the morning is usually normal; in the great majority of cases, however, persistent bad breath originates in the mouth. The most common causes are the bacterial coating on the tongue and gum disease. Treatment for bad breath relies on correctly identifying the source and treating that source.
What causes bad breath?
The main source of bad breath is volatile sulfur compounds produced by certain bacteria in the mouth as they break down proteins in food debris and tissue remnants. These compounds form especially in areas where oxygen is scarce and bacteria can multiply easily: the back of the tongue, periodontal pockets and hard-to-clean spaces between the teeth.
Morning breath is related to reduced saliva flow during sleep and usually decreases after brushing, tongue cleaning and breakfast. Going without food for a long time, talking a lot and certain foods can also cause temporary odor. Odor that lasts all day or is noticed by people around you, however, is something that should be evaluated.
Halitosis is generally divided into three groups according to its source: halitosis originating in the mouth, halitosis originating outside the mouth, and pseudohalitosis, in which a person believes they have bad breath even though there is no odor. This distinction needs to be made for treatment to be appropriate. In pseudohalitosis, the examination findings are explained to the person and guidance on oral care is provided; if the concern is marked, a referral for appropriate support may be made.
What are the causes inside the mouth?
- Tongue coating: Bacteria, shed cells and food debris that build up on the back of the tongue are one of the most common sources.
- Gum disease: Gingivitis and especially periodontitis.
- Decayed teeth and defective fillings: These create areas where food debris accumulates.
- Dentures and bridges: Removable dentures that are not cleaned well enough and the areas under bridges.
- Dry mouth: Reduced saliva flow due to medications, mouth breathing or insufficient fluid intake.
- Inflammation around implants: For details, see our peri-implantitis treatment page.
- Wisdom teeth: Inflammation that develops around partially erupted teeth.
More than one of these causes may be present in the same person. For example, in someone with both a heavy coating on the tongue and gum inflammation, treating only one of them may not be enough; this is why all possible sources are assessed together during the examination.
How does gum disease cause bad breath?
In periodontitis, the deep pockets that form between the tooth and the gum provide a suitable habitat for bacteria that thrive without oxygen. These bacteria produce sulfur compounds, and the inflammation and tissue breakdown inside the pocket also contribute to the odor. Because a toothbrush and floss cannot reach the depths of these pockets, mouthwashes and breath mints can only mask the odor for a short time.
If the source is periodontal, gum disease treatment followed by regular maintenance visits plays a central role in controlling bad breath.
How is bad breath evaluated?
The evaluation begins with a detailed conversation: you are asked how long the odor has been present, who noticed it, at what times of day it gets worse, what medications you take, and about your general health, diet and smoking habits. Then the surface of the tongue, gum measurements, decay, fillings, dentures and saliva flow are examined.
Breath odor can be evaluated by the clinician smelling it directly (organoleptic assessment); in some cases, devices that measure sulfur compounds may be used. For a more accurate assessment, you may be asked not to use perfume, eat foods such as garlic and onions, use mouthwash or smoke in the hours before your appointment.
How is bad breath treated?
Tongue cleaning
Because the coating on the back of the tongue is one of the most common sources, tongue cleaning is an important part of treatment. Cleaning once or twice a day with a tongue scraper or tongue brush, using gentle back-to-front strokes, is recommended. To avoid triggering the gag reflex, it can help to stick your tongue out and not start the cleaning too far back. The correct technique is demonstrated during the examination.
Professional cleaning and periodontal treatment
Plaque and tartar on the tooth surfaces are removed with scaling and root planing. If periodontitis is detected, stepwise periodontal treatment is planned. When the periodontal pockets are cleaned, the bacterial load that is the source of the odor decreases; to maintain the result, plaque must be kept from building up again inside the pockets and regular check-ups are needed.
Addressing other sources inside the mouth
Decay is treated, defective fillings and crowns are replaced, and the cleanliness and fit of dentures are assessed. If you have dry mouth, measures such as drinking enough water and chewing sugar-free gum are recommended; it may be necessary to consult the relevant physician about medications that can cause dryness.
Supportive products
Mouthwashes containing chlorhexidine, cetylpyridinium chloride or zinc may be recommended as short-term support; however, they do not replace mechanical cleaning. Because long-term use of chlorhexidine can cause staining of the teeth and changes in taste, it should be used on a clinician's recommendation and for a limited period.
Can bad breath be a sign of another disease?
Yes; although less often, the source of bad breath can lie outside the mouth. These causes include nose and sinus inflammation, tonsil problems and tonsil stones, respiratory tract infections and digestive conditions such as reflux. Certain general health problems, such as uncontrolled diabetes and kidney and liver disease, can also cause distinctive odors on the breath. Some foods and drinks, such as garlic, onions and alcohol, can also cause temporary odor by passing into the bloodstream and being exhaled with the breath. For more on the relationship between oral and general health, see our article on gum disease and general health.
If no source that explains the odor is found in the mouth, or if the odor persists despite treatment inside the mouth, you are referred to the relevant specialties, such as ear, nose and throat (ENT), gastroenterology or internal medicine, to look into possible causes outside the mouth.
How long does the treatment process take?
The length of treatment varies according to the source of the bad breath. In cases caused by the coating on the tongue, a difference may be noticed within a short time with regular tongue cleaning. If the source is periodontal, stepwise gum treatment and the healing process can take a few weeks, followed by a re-evaluation. In cases caused by decay, fillings or dentures, the time depends on the scope of the dental treatment needed. After treatment, follow-up appointments are scheduled to evaluate and maintain the result.
What can I do to prevent bad breath?
- Brush twice a day with fluoride toothpaste for about two minutes.
- Clean between your teeth every day with floss or an interdental brush.
- Add tongue cleaning to your daily routine.
- Drink enough water during the day; try not to go without food for long periods and limit sugary drinks.
- If you smoke, get support to quit.
- Clean your removable dentures every day.
- Have regular dental check-ups.
For the correct techniques, read our guide to proper brushing and interdental cleaning. If your bad breath persists despite these measures, it is advisable to see your dentist.
