Bad breath from inflamed gums: where the smell actually comes from

The smell is not coming from your stomach. In the great majority of cases, persistent bad breath (Mundgeruch) is produced in the mouth itself, by bacteria that break down protein and release sulphur gases as they do it. Inflamed gums (Zahnfleischentzündung) are one of the two classic sources, because the space between an inflamed gum and the tooth is warm, low in oxygen and supplied with exactly the protein those bacteria prefer. The other is the coating on the back of the tongue. Both are treatable, and neither responds for long to mints, gum or mouthwash, which mask an odour that returns within the hour. The useful step is working out which source is yours — and there is a fifteen-second test below that points to the gums specifically.

Bacteria that thrive without oxygen — anaerobes — feed on protein. Breaking down its amino acids releases volatile sulphur compounds: hydrogen sulphide, which smells of rotten eggs, and methyl mercaptan, closer to old cabbage. The human nose detects these at astonishingly low concentrations, which is why a small amount of the right bacteria in the right place has such a disproportionate effect.

An inflamed gum is a near-perfect home for them. The margin lifts slightly away from the tooth into a sheltered groove where oxygen barely reaches; inflamed tissue leaks fluid and a little blood, and blood is protein; cells shed from the lining add more. The result is a warm, moist, protein-rich, oxygen-poor niche — a small fermentation chamber running quietly against the tooth.

That explains the pattern people describe: worst on waking and after hours without food or drink, when saliva flow is low; back within thirty to sixty minutes of brushing, because brushing clears the gas but not the pocket producing it; often alongside a stale or metallic taste, which is the same chemistry noticed from the inside. Deeper pockets house more anaerobes and smell stronger — Gingivitis or periodontitis: the difference that decides everything sets out that distinction.

The olfactory system stops reporting a constant background smell within minutes — a useful adaptation that makes self-assessment nearly impossible. People with strong halitosis often have no idea; people with perfectly ordinary breath can be convinced they have a problem. Cupping your hands over your mouth settles nothing; that mostly tests the air in your hands.

The floss test — the one that points to the gums. Pass floss or an interdental brush between two back teeth, take it out, and smell it after about ten seconds. Repeat in a different area. Healthy gaps smell of essentially nothing, so if one particular gap produces a distinct odour you have localised the source — and it is dental, not digestive.

The tongue test. Scrape the back third of the tongue with a plastic spoon, let the material dry for half a minute, then smell it. A strong odour here points to tongue coating instead: different problem, different solution.

The honest witness. A partner or close friend, asked in the morning before coffee. Awkward for ten seconds, and more reliable than any home method.

If the floss smells and the spoon does not, your gums are the source. If both smell, you have both — which is very common.

Two of those deserve a note. The stomach is almost never the cause — the oesophagus is normally closed, and continuous odour from it requires an actual medical condition such as significant reflux. And garlic breath is exhaled, not chewed: its sulphur compounds are absorbed in the gut, carried in the blood and released by the lungs, which is why it outlasts brushing by hours. That is physiology, not a hygiene failure.

Very occasionally a distinctive smell points elsewhere — a sweet, acetone-like breath in poorly controlled diabetes, for instance. Persistent odour with no dental finding is worth mentioning to your GP (Hausarzt).

Because none of them touches the source. A mint adds a smell on top of a smell. Chewing gum stimulates saliva, which genuinely helps if dryness is the problem, but does nothing about a pocket. Mouthwash lowers the bacterial count on surfaces for a few hours without penetrating the biofilm below the gum margin, and high-alcohol rinses dry the mucous membrane, which can leave breath slightly worse later.

There is one useful signal in all this: if a mouthwash helps for two hours and then everything returns exactly as before, the source is mechanical and still in place.

Clean between the teeth every day. The gaps are where the anaerobes live and where a toothbrush has never been. For most people this one change does more than every product they have bought.

Clean the tongue, properly. A tongue scraper or the back of a spoon, not a toothbrush: four or five gentle strokes from as far back as you can comfortably reach towards the front, rinsing between, before you brush. If you gag, start further forward and work back over a week — the reflex settles with practice.

Have the deposits removed. Hardened tartar (Zahnstein) below the gum margin cannot be brushed off. A professional cleaning (professionelle Zahnreinigung, PZR) removes it and lets the gum reattach; where pockets have formed, a course of gum treatment addresses what lies deeper. This is the step that most often ends a long-standing problem — usually a private service, though many statutory funds contribute something, so ask yours.

Fix the traps. A broken filling edge, an open crown margin, a gap where food packs daily: each is a small repair with a disproportionate effect.

Keep the mouth wet, and stop smoking. Water through the day, sugar-free gum after meals, less alcohol and caffeine in the evening. If a medication is drying your mouth, say so. Smoking adds its own odour, dries the mouth and drives the gum inflammation underneath.

Do not spend six months buying products. Persistent bad breath has a physical cause in the mouth in the overwhelming majority of cases, and finding it usually takes one examination.

Fasting and low-carbohydrate diets. Both reduce saliva flow and change metabolism; keto diets produce a characteristic acetone note that brushing does not remove. During Ramadan, hours without water leave the mouth dry from midday onwards — cleaning thoroughly before the fast begins and after it ends makes a noticeable difference, and untreated gum inflammation makes those hours considerably worse.

Braces and aligners. Fixed braces (feste Zahnspange) hold food and plaque around every bracket. Clear aligners (Aligner) need rinsing each time they come out: an aligner put back over unbrushed teeth after lunch seals a warm layer of bacteria against the enamel for hours.

A dry mouth, from medication or from breathing through it. Antidepressants, antihistamines, blood pressure tablets and diuretics all reduce saliva — the mouth’s own rinse — and so does sleeping with an open mouth. Less saliva means more odour, more plaque and more decay. Bring your medication list.

You are new to Germany. Bad breath is hard to raise with anyone, harder still in a second language with a stranger in a white coat. It is an ordinary clinical finding with an ordinary clinical answer, and you can describe it in English here. English-Speaking Dentist in NRW explains how a first appointment works and what your health insurance card (Gesundheitskarte) covers.