Occasional bad breath is universal: garlic at lunch, a strong coffee, the morning after a late night. Persistent bad breath is different, and it deserves proper investigation rather than stronger mints. The causes of persistent bad breath are almost always findable, usually located in the mouth, and in most cases entirely treatable.
Before anything else: this is not a hygiene failure, and plenty of scrupulous brushers have it.
On this page
- Where the smell actually comes from
- Cause one: gum disease
- Cause two: tongue coating
- Cause three: dry mouth
- Cause four: food traps and dental work
- Other causes in the mouth
- Causes outside the mouth
- What to do about it
- In summary
Where the smell actually comes from
Almost all breath odour is produced by bacteria breaking down proteins and releasing volatile sulphur compounds. Those compounds are what we smell.
So the practical question is always the same: where in your mouth are bacteria sheltering undisturbed with a supply of protein? Answer that and you have found the cause.
Around eighty to ninety per cent of persistent bad breath originates in the mouth, which is encouraging, since that is where it can be dealt with.
Cause one: gum disease
One of the most common causes, and one of the most treatable.
When gums become inflamed, pockets form between gum and tooth. Those pockets are precisely the environment odour-producing bacteria thrive in: sheltered, low in oxygen, and beyond the reach of any toothbrush.
Persistent bad breath is one of gum disease’s classic signs, and sometimes the only one a patient notices, since the condition is largely painless. Our post on why gums bleed when you brush covers the other warning sign, and our page on gum disease treatment explains what treatment involves.
The good news is a double win: treating the gums clears the breath and saves the teeth.
Cause two: tongue coating
The other leading cause, and the most commonly overlooked.
The back of the tongue is a rough landscape of grooves that traps debris, dead cells and bacteria, and it is furthest from the cleansing action of saliva. For many people, cleaning it makes a genuinely dramatic difference within days.
Our post on whether you should clean your tongue explains exactly how to do it, and it takes about ten seconds a day.
Cause three: dry mouth
Saliva is your mouth’s rinse cycle. It washes away debris, neutralises acids and carries antibacterial components. Reduce it, and odour builds unchecked.
This is why morning breath exists: saliva flow drops overnight. It is also why persistent dry mouth causes persistent bad breath.
Common causes include many everyday medications, particularly those for blood pressure, mood and allergies, mouth breathing and snoring, dehydration, alcohol, smoking, and some medical conditions.
Do not stop any medication on your own account. Mention it, and where a review might help, your GP can be involved.
Cause four: food traps and dental work
Anywhere food lodges and sits is a source: gaps between teeth, cavities, the margins of ageing fillings and crowns, and beneath bridges.
Old dental work that no longer seals properly is a particularly common culprit, because the trap is invisible and the patient cannot clean it out. Our post on what tartar is explains another deposit that harbours odour-causing bacteria and cannot be brushed away.
Other causes in the mouth
- Dentures that are not cleaned thoroughly, or worn overnight. Our post on whether to sleep in dentures covers this.
- Tonsil stones, small calcified deposits in the tonsils which produce a distinctive and unpleasant odour.
- Smoking, which contributes directly and dries the mouth.
- Untreated decay, particularly deep cavities.
Causes outside the mouth
Less common, but worth knowing about if a thorough dental assessment finds nothing.
Sinus and throat infections, post-nasal drip, acid reflux, and occasionally conditions affecting the lungs, liver, kidneys or blood sugar can all affect breath. Some produce characteristic odours a doctor would recognise.
Certain foods also work systemically rather than locally: garlic and onions are absorbed and exhaled from the lungs for many hours, which is why brushing does not touch them.
If your mouth is genuinely healthy, the honest next step is your GP rather than more dental treatment.
What to do about it
- Get an assessment. Gums measured, tongue examined, teeth and dental work checked, dry mouth and medications reviewed. The cause has to be found before it can be treated.
- Clean between your teeth daily. Where a brush cannot reach is where the problem usually lives.
- Clean your tongue daily, gently and as far back as comfortable.
- Have professional cleaning to remove the tartar and plaque below the gum line that home care cannot reach.
- Stay hydrated, sipping water through the day.
- Treat mints and mouthwash as a top-up, not a solution. If you always need the next one, the cause is untreated.
Our page on fresh breath treatment explains the assessment, and a hygiene appointment is often the right first step. The NHS page on bad breath has further guidance.
In summary
Persistent bad breath is caused by bacteria producing sulphur compounds, and the usual homes are gum pockets, the back of the tongue, dry mouth and food traps around teeth and dental work. It is not a reflection on your brushing, and in most cases the cause is findable and treatable.
It is a far easier conversation than you are imagining. Ring us on 01255 422506, and if you would rather ask in writing first, our Ask the Dentist page exists for exactly that.
This article is general information rather than personal dental advice. Every mouth is different, so please speak to your dentist about your own teeth.