Bad breath (halitosis): causes and what helps

Being afraid to talk to people up close, or an awkward remark from someone close to you: bad breath (halitosis) is common. A Cochrane review estimates that 50 to 60 percent of the world's population has experienced it (Kumbargere Nagraj et al., 2019, PubMed), and a meta-analysis found it in 31.8 percent of teenagers and adults (Silva et al., 2017, PubMed). This guide explains where bad breath comes from, how to know if you have it, what you can do and when to see a dentist or a doctor. It is here to inform you; it does not replace an examination.

What causes bad breath?

In the vast majority of cases: the mouth

Contrary to a widespread belief, bad breath rarely comes from the stomach. An international consensus workshop points out that, in people who seek help for it, the source is in the mouth in about 90 percent of cases (Seemann et al., 2014, PubMed). In a specialist clinic in Belgium that examined 2,000 patients, a cause in the mouth was found in 76 percent of them: a coating on the tongue (43 percent), gum disease (11 percent) or both (18 percent); a cause in the ear, nose and throat or elsewhere in the body was found in only 4 percent (Quirynen et al., 2009, PubMed).

The smell mainly comes from sulphur compounds: bacteria that live without oxygen break down leftover proteins and release gases that smell of rotten eggs. The coating on the back of the tongue is considered their main source (Tangerman and Winkel, 2010, PubMed).

The most common causes in the mouth:

Tongue coating: a white or yellowish layer at the back of the tongue.
Plaque and tartar: plaque that is not removed hardens into tartar, which a toothbrush can no longer remove (see the scale and polish guide).
Gum disease: inflamed gums, or the pockets of periodontitis, shelter these bacteria (see the gum disease guide).
Decay and old fillings: food gets trapped in a cavity or under a filling that no longer seals well.
Dentures and bridges: a removable denture that is not cleaned well or is worn at night, or a bridge that traps food (see crowns, bridges and dentures).
A partly erupted wisdom tooth, whose gum flap traps debris (see wisdom teeth).
Dry mouth and smoking.

Less often: the nose, the throat, the stomach or a general illness

Causes outside the mouth account for about 5 to 10 percent of cases, but they can be a sign of a serious illness (Tangerman and Winkel, 2010, PubMed):

The nose and sinuses: long-lasting sinusitis, mucus dripping down the back of the throat.
The tonsils: tonsillitis, or small whitish, foul-smelling deposits lodged in their crevices (tonsil stones).
The stomach: a recent meta-analysis found a link between the stomach bacterium *Helicobacter pylori* and bad breath; but these are observational studies, which do not prove that the stomach is the cause in any given person (Xia et al., 2026, PubMed).
A general illness (poorly controlled diabetes, kidney, liver or lung disease): the smell is then often unusual and comes with other signs.
Some medicines, especially those that dry the mouth (Iranitalab et al., 2026, PubMed). Never stop a treatment on your own: talk to your doctor.

Garlic, onion, spices and coffee cause a temporary smell that goes away within a few hours.

What you notice	Possible source
Stronger smell in the morning, white coating at the back of the tongue	Tongue coating, dry mouth at night
Gums that bleed, loose teeth	Gingivitis or periodontitis
Bad taste in one spot, food getting stuck	Decay, old filling, wisdom tooth
Smell when breathing out through the nose with the mouth closed	Nose or sinuses
Small white, smelly lumps in the throat	Tonsils
Heartburn, acid coming back up	Stomach (to discuss with a doctor)

Morning breath, Ramadan fasting and dry mouth

Bad morning breath is normal: during sleep you make much less saliva, and the bacteria on the tongue are left undisturbed. It goes away after breakfast, brushing and cleaning your tongue.

During Ramadan, going without food or drink for long hours dries the mouth, and saliva no longer cleans it. In a study of 278 fasting adults in Bangladesh, 45.4 percent said they sometimes had bad breath and 32.7 percent regularly; only 10.4 percent cleaned their tongue every day (Mahmud et al., 2026, PubMed). What helps:

brushing your teeth and cleaning your tongue after iftar and after suhoor, and flossing in the evening;
drinking water regularly between iftar and suhoor, rather than sugary drinks or coffee;
if you use a miswak (siwak), keeping it as an extra, without replacing your toothbrush and fluoride toothpaste.

Everyday dry mouth (mouth breathing, stress, age, some medicines or illnesses) also makes breath worse. If it is constant, talk to your dentist or doctor.

How to know if you have bad breath

We get used to our own smell: breathing into your hands does not give a reliable answer. More useful:

ask someone you trust, up close, while talking normally;
wipe a clean spoon over the back of your tongue and smell it after a few seconds;
look at your tongue: a thick coating at the back is a clue.

At the dentist, the reference method is still the smell judged by an examiner; measuring devices only partly agree with it (Szalai et al., 2023, PubMed). Some people are convinced they have bad breath when nobody can smell it: this was the case for 16 percent of the Belgian patients (Quirynen et al., 2009, PubMed). An examination can check and reassure.

How to get rid of bad breath

The principle: treat the source, which is usually in the mouth.

Brush your teeth twice a day, for two minutes, with a fluoride toothpaste, paying attention to the gum line.
Clean your tongue every evening, from back to front, gently, with a tongue cleaner or your toothbrush. The Cochrane review finds that trials of tongue cleaning are still few and of low quality (Kumbargere Nagraj et al., 2019, PubMed), but it targets the main source of the smell directly.
Clean between your teeth every day, with floss or interdental brushes, whose size you choose with your dentist.
Drink water and do not skip breakfast.
Stop smoking: your doctor or pharmacist can help.
Clean removable dentures every day.
See your dentist: a scale and polish, gum treatment, filling cavities and replacing leaking old fillings often remove the source.

Mouthwash and chewing gum: why they only mask it

Scented mouthwashes, chewing gum and sprays feel fresh, but they do not remove the tongue coating, the tartar or the food trapped in a cavity: when their effect wears off, the smell comes back. The Cochrane review, which brought together 44 trials (mouthwashes, toothpastes, chewing gum, tongue cleaning and more), found low to very low certainty evidence, and could not say that any product was better than another (Kumbargere Nagraj et al., 2019, PubMed).

An antiseptic mouthwash sometimes has a place, for a limited time and on your dentist's advice, but it can hide gum disease that keeps progressing. The same goes for home remedies and herbs: they do not treat the source and can delay a visit.

When to see a dentist

Book an appointment if:

bad breath lasts more than two weeks despite good brushing and tongue cleaning;
your gums bleed or teeth are loose;
you have a bad taste in one spot, pain or pus;
the smell seems to come from a denture, a bridge or a wisdom tooth;
your last check-up was a long time ago.

If you have facial swelling, fever, or difficulty swallowing or breathing, go to the emergency department straight away (see toothache).

When to see a doctor

If the dentist finds no cause in the mouth, or if other signs come with it, see a doctor:

blocked nose, thick discharge, facial pain that lasts;
sore throat with fever, or smelly deposits that keep coming back in the tonsils;
heartburn, acid reflux, stomach pain, vomiting or black stools;
a cough that lasts, phlegm, breathlessness, or weight loss and fever that last;
an unusual smell: a fruity smell with intense thirst, passing urine often and weight loss (diabetes must be checked for quickly), a smell of urine in someone with kidney disease, an unusual smell with jaundice;
a sore in the mouth that does not heal within two to three weeks.

Go to the emergency department if a fruity smell comes with vomiting, drowsiness or difficulty breathing.

Booking an appointment

Consultations take place in Rabat, Monday to Friday from 9 am to 6 pm and on Saturday from 9 am to 2 pm; the address is given when you book. The easiest way is to send a WhatsApp message saying how long the bad breath has lasted and whether your gums bleed. See the appointment section.

Frequently asked questions

How do I get rid of bad breath?

By treating its source, which is in the mouth in the vast majority of cases: brushing twice a day with a fluoride toothpaste, cleaning your tongue every evening, floss or interdental brushes, drinking water, stopping smoking, then an examination at the dentist for a scale and polish and any treatment needed; if nothing is found in the mouth, a doctor looks for another cause.

Can bad breath come from the stomach?

It can, but much less often than people think, since the source is in the mouth in about 90 percent of people who seek help; talk to your doctor about your stomach especially if you have heartburn, acid reflux or stomach pain, after having your mouth examined.

Does Helicobacter pylori cause bad breath?

Studies show a link between this stomach bacterium and bad breath, and breath may improve once it is treated, but they do not prove it is the cause in a given person; only a doctor can test for it and decide on treatment, and the mouth should be examined first, as it is by far the most common source.

Why do I have bad breath even though I brush?

Often because the tongue is not cleaned, the spaces between the teeth are missed, or tartar, gum disease, a cavity or an old filling are holding bacteria where the brush cannot reach; dry mouth, smoking or a cause in the nose or throat are also possible.

Can tonsillitis or tonsil stones cause bad breath?

Yes: an infected throat or small deposits in the crevices of the tonsils can smell strongly; do not dig them out with sharp objects, and see a doctor if they keep coming back or if you have a sore throat with fever.

Can wisdom teeth cause bad breath?

Yes, especially a partly erupted wisdom tooth: food and bacteria get trapped under the gum flap, which can become inflamed; your dentist can clean the area and discuss whether the tooth should be removed.

My child has bad breath: what should I do?

In children, the causes are mostly in the mouth (not enough brushing, tongue coating, decay, inflamed gums), as well as mouth breathing (Bawazir, 2021, PubMed); help them brush their teeth and tongue with an amount of fluoride toothpaste suited to their age, avoid sweet drinks in a bottle at night for toddlers, have their teeth checked, and see a doctor if they have a blocked nose or discharge from one side of the nose only, which can be a sign of a small object stuck inside.

Can bad breath come back after treatment?

Yes, if the cause comes back: the tongue coating forms again every day, and tartar or gum inflammation return when cleaning slips; daily cleaning and regular check-ups help keep it under control.