The chemistry, in one paragraph
Certain bacteria in the mouth are anaerobic: they thrive where there is little oxygen. Their food is protein — from food remnants, from shed cells, from blood and from the fluid that seeps out of inflamed gums. Breaking it down releases volatile sulphur compounds, usually abbreviated to VSCs. Hydrogen sulphide gives the classic rotten-egg note; methyl mercaptan smells of decay and is strongly associated with gum disease; dimethyl sulphide tends to point away from the mouth and towards a systemic source. Halitosis is essentially a question of where in your mouth those anaerobes have found somewhere airless to live.
Ranking the sources — most to least common
1. The coating on the back of the tongue. By some distance the most common source. The rear third of the tongue has deep grooves and papillae, no self-cleaning mechanism and very little oxygen. A visible white or yellowish film there is a bacterial mat producing VSCs all day. It is also the part of the tongue almost nobody cleans, because it triggers the gag reflex.
2. The spaces between the teeth. Airless, protein-rich, and unreachable by a toothbrush. If your floss smells when you use it between two particular teeth, you have located a source precisely.
3. Gum pockets. Where gums are inflamed and have detached slightly from the tooth, the pocket is a perfect anaerobic chamber. Periodontitis (Parodontitis) has a characteristic smell, and it is the reason bad breath and bleeding gums so often arrive together.
4. Tartar, above and below the gum. Its role is structural. The deposit is porous and rough, so it holds many times more biofilm than smooth enamel; below the gum, the deposits keep pockets open and inflamed. Removing it eliminates the shelter, which is why breath often improves markedly after a thorough cleaning.
5. Food traps in the dental work. Untreated decay, a leaking filling, a gap under an old crown, a denture (Prothese) that is not cleaned daily, or a partly erupted wisdom tooth (Weisheitszahn) with a flap of gum trapping debris underneath.
6. A dry mouth. Saliva is the mouth’s rinse and its oxygen supply. Less of it means more anaerobic activity — which is exactly why morning breath exists in people with perfectly healthy mouths.
What is normal, and what is not
Morning breath is physiological. Saliva flow drops during sleep, bacteria multiply undisturbed, and everyone wakes up with it. It disappears after brushing and breakfast, and it is not halitosis.
Garlic, onion and alcohol are not an oral hygiene problem. Their sulphur compounds are absorbed into the bloodstream and exhaled from the lungs for many hours afterwards. Brushing will not shorten that; only time will.
How to find out where yours is coming from
You cannot smell your own breath. The olfactory system adapts to constant input within minutes, so your own smell becomes invisible to you — which is why the question is so anxiety-provoking and why people either dismiss a real problem or worry about one that is not there.
Three tests that work reasonably well at home:
The floss test. Pass floss between two back teeth, take it out, wait a moment and smell it. Do it in several places. This localises the problem, which the other tests do not.
The spoon test. Scrape the back of your tongue with a plastic spoon, let the deposit dry for a few seconds, then smell it. If that is the source, this is unambiguous.
The wrist test. Lick the back of your wrist, let it dry for ten seconds, smell it. It samples the front of the mouth only, so a negative result here does not rule much out.
When it is not your mouth at all
A minority of cases originate elsewhere, and dentistry cannot solve those. Worth considering if a thorough cleaning and a proper tongue routine change nothing:
Tonsil stones (Mandelsteine). Small whitish lumps of debris in the crypts of the tonsils, and they smell strongly out of all proportion to their size. Common, harmless, often overlooked. An ENT specialist can advise if they recur.
Sinus problems and post-nasal drip. Chronic sinusitis or persistent nasal drip delivers protein-rich mucus to the back of the throat, where the same anaerobes go to work. Also worth mentioning: habitual mouth breathing dries the mouth and worsens everything above.
Dry mouth from medication. Very common and much underestimated. Many blood pressure tablets, antidepressants, antihistamines and diuretics reduce saliva flow. Do not stop anything on your own; discuss it with the prescribing doctor, and in the meantime raise your fluid intake and use sugar-free gum.
Reflux. Stomach acid reaching the oesophagus can produce both odour and enamel erosion on the inner surfaces of the teeth — a pattern a dentist sometimes spots before the patient makes the connection.
Diet and metabolism. Strict low-carbohydrate diets produce acetone, a sweetish, nail-varnish note that is harmless. Uncontrolled diabetes and liver or kidney disease each produce characteristic odours; if your breath changes alongside thirst, weight change or fatigue, that belongs with your GP (Hausarzt) rather than your dentist.
“It’s my stomach” is usually wrong. The oesophagus is normally closed; smells do not rise freely from the stomach. It is one of the most common misattributions in dentistry, and it sends people to the wrong specialist for years.
The order to tackle it in
Working through this sequence solves the large majority of cases.
1. Clean the back of the tongue, daily. A scraper is better than a brush. Start further forward than feels useful and work back a little each day; the gag reflex desensitises within a week or two. This single change fixes more bad breath than anything else on the list.
2. Clean between the teeth, daily. Interdental brushes (Interdentalbürsten) where the gaps allow, floss where they do not.
3. Deal with dry mouth. Water through the day, sugar-free gum after meals, and avoid alcohol-based mouthwashes, which dry the mouth further and can make the problem worse in the medium term.
- 4. Have the tartar removed and the gums measured. This clears the sheltered surfaces and, just as importantly, establishes whether there are pockets underneath — and it is the appointment where decay, leaking fillings and old margins get checked as well. Subgingival deposits are not reachable at home by any method: Can you remove tartar yourself?
- Professional cleaning (PZR) – service page (EN).
5. Use rinses as support, never as the answer. Zinc-containing rinses neutralise sulphur compounds chemically rather than masking them, which is a real advantage. Chlorhexidine is effective but for short courses only, on a dentist’s advice, since prolonged use stains the teeth and alters taste. Mints do nothing but buy twenty minutes.
6. If none of that changes anything, look beyond the mouth — ENT first, then your GP.
What your insurance covers
Do not leave the bonus booklet (Bonusheft) empty. A stamp at each annual check-up costs nothing and decides your fixed subsidy (Festzuschuss) if you ever need a crown, bridge or denture: 60 % of standard care without a full record, 70 % after five unbroken years, 75 % after ten, and up to 100 % under the hardship provision (Härtefallregelung). A single missed year resets the count.
When to have it looked at
If you have just moved to Germany
Bad breath is an awkward subject in any language and considerably more so in a second one. Two practical notes. First, nobody reminds you about the annual check-up here — you book it yourself, and it is the appointment where the covered scaling happens. Second, tongue scrapers, interdental brushes and zinc rinses are all sold in any drugstore (dm, Rossmann) and pharmacy (Apotheke), no prescription needed.
Our team treats patients in English, so you can describe the problem in your own words rather than in improvised German: English-Speaking Dentist in NRW.
It often improves it substantially, because it removes the deposits and biofilm that shelter the odour-producing bacteria, including below the gum line where you cannot reach. Whether it solves the problem entirely depends on the source: if the main site is the tongue coating, cleaning helps but the daily tongue routine is what settles it.
Your sense of smell adapts to a constant stimulus within a few minutes, so your own odour effectively disappears for you. This is why the floss and spoon tests, or an honest second opinion, are more reliable than trying to judge for yourself.
Both types exist. Most fresh-breath rinses mask for twenty minutes or so. Zinc-containing rinses genuinely bind the sulphur compounds. Alcohol-based rinses can make matters worse over time by drying the mouth, and no rinse reaches into gum pockets or under tartar.
Almost certainly not. The oesophagus stays closed between swallows, so odours do not travel up from the stomach in the way people imagine. Reflux is the exception. If everything in the mouth is healthy, tonsil stones, sinus problems and dry mouth are the far likelier explanations.
They are small, soft, whitish accumulations of debris and bacteria in the crevices of the tonsils. Their smell is very strong for their size. You may occasionally cough one out, or see white specks at the back of the throat. They are harmless, but if they recur an ENT specialist is the right person to ask.
Tartar plays a genuine part in bad breath, but as a shelter for the bacteria rather than as the smell itself — which is why removing it helps and rarely solves the problem alone. Clean the back of your tongue every day, clean between your teeth every day, keep your mouth from drying out, and have the deposits and gum pockets dealt with professionally. If all of that is in place and the smell persists, the source is probably not your teeth, and that is useful information rather than a dead end.
Zahnarztpraxis Tsypin · Wuppertal. This article was medically reviewed and is provided for information; it does not replace an examination. Updated August 2026.
