Bad breath is unpleasant, yet rarely discussed openly – not even with the dentist. But in the vast majority of cases the cause can be found and treated specifically.
Where the smell comes from
About 90 percent of all cases of bad breath (halitosis) actually originate in the mouth itself – the remaining roughly 10 percent trace back to conditions in the ear, nose and throat area or the digestive tract. Within the mouth, by far the most common source is coating on the tongue: certain bacteria on the back of the tongue break down protein residues and release foul-smelling sulphur compounds in the process. People with pronounced bad breath have demonstrably far more of these bacteria on their tongue than people without.
The second most common cause is untreated gingivitis or periodontitis: inflamed gum pockets provide ideal conditions for the same odour-causing bacteria. Leaking crown margins, deep decay, or poorly fitting dentures can also form niches where plaque accumulates.
What helps against the most common causes
- Clean your tongue too. A tongue scraper or the bristles of your toothbrush, guided gently front-to-back over the back of the tongue once a day, noticeably reduces the bacterial load. Scraping too hard just irritates the tongue unnecessarily.
- Don't forget the spaces between teeth. It's precisely where the brush can't reach that plaque forms, leading to odour and gum inflammation. Details in our guide to cleaning between your teeth.
- Drink enough. A dry mouth encourages bacterial growth, because there's less saliva available to rinse and neutralise. That also explains why bad breath is usually strongest in the morning.
- Get bleeding gums checked instead of ignoring it – it's a warning sign of inflammation that can also contribute to the odour.
For persistent bad breath, we advise against mouthwashes and gum that only mask the smell – they treat the symptom, not the cause, and often just delay someone looking at the actual source.
When a dental check-up makes sense
If persistent bad breath doesn't improve within a few weeks despite thorough cleaning of teeth, interdental spaces and tongue, a professional cleaning with a thorough check-up is worthwhile. That's where we find hidden gum pockets, leaking filling margins or early decay that isn't noticeable from the outside.
If the odour persists despite an unremarkable dental finding, a cause outside the mouth should also be considered – for instance in the ENT or digestive area. In that case, your GP is the right next point of contact.
In short: in nine out of ten cases the cause is in the mouth – usually on the tongue, often combined with the spaces between the teeth or the gums. Clean the tongue too, clean between the teeth, drink enough. If the odour persists anyway, a thorough dental check-up helps.