SymptomMouth & teeth
Bad Breath: Causes and How to Get Rid of It
Bad breath is an unpleasant odor from the mouth. In about 9 out of 10 people it starts in the mouth itself, where bacteria on the back of the tongue, between teeth and in gum pockets break down food and dead cells and release sulfur gases. Dry mouth, gum disease, smoking and strong foods make it worse. Cleaning the tongue, flossing and treating gum disease fix most cases. Less often, the cause is the tonsils, sinuses, stomach or a medical condition.
Also called: Halitosis, foul breath, mouth odor
At a glance
- What it is
- A persistent unpleasant mouth odor. The medical term is halitosis.
- Main source
- Bacteria on the back of the tongue and in gum pockets.
- Common triggers
- Poor tongue and gum cleaning, dry mouth, smoking, garlic and onions, dieting.
- Medical causes
- Gum disease, tonsil stones, sinusitis, reflux, uncontrolled diabetes, liver or kidney failure.
- Treatment
- Tongue cleaning, flossing, dental care, and treating any underlying cause.
When to get help
Call 911 or go to the ER
- Fruity-smelling breath with heavy breathing, vomiting, confusion or drowsiness, especially in someone with diabetes (possible ketoacidosis)
See a doctor within a day or two
- Bad breath with a painful swollen gum, face or jaw and fever (possible dental abscess)
- Bad breath with a severe one-sided sore throat and difficulty opening the mouth
- Breath that smells of urine or ammonia, or a musty, sweet smell, with new tiredness, swelling or yellow skin
Book a routine appointment
- Bad breath that persists despite good brushing, flossing and tongue cleaning for 2 weeks
- Bleeding, receding or tender gums, or loose teeth
- Foul-smelling nasal discharge or white lumps in the tonsils
Usually safe to manage at home
- Morning breath that clears after brushing and breakfast
- Bad breath after garlic, onions, coffee, alcohol or smoking
How to tell if you have bad breath
People are poor judges of their own breath because the nose adapts to it. Ways to check:
- Ask someone you trust.
- Lick the inside of your wrist, wait 10 seconds and smell it.
- Gently scrape the back of your tongue with a spoon and smell the residue. This represents the main source of odor.
Some people are convinced they have bad breath when others notice nothing. This is called halitophobia and can cause real distress. A dentist can assess breath objectively.
Causes of bad breath
Mouth causes (about 90% of cases)
- Tongue coating: the back of the tongue holds bacteria and debris. This is the single biggest source.
- Gum disease: bacteria in pockets between gums and teeth produce strong odors. Bleeding gums and receding gums are clues. Advanced periodontitis causes loose teeth.
- Food between teeth and under bridges or dentures not cleaned daily.
- Tooth decay and dental abscesses.
- Dry mouth: saliva rinses away bacteria. Dry mouth from sleep, mouth breathing, medicines (antidepressants, antihistamines, diuretics), Sjögren's syndrome or radiation causes odor.
Lifestyle causes
- Smoking and vaping
- Garlic, onions and spices, whose odor compounds are absorbed into blood and exhaled from the lungs for up to a day or more
- Alcohol and coffee
- Fasting or low-carbohydrate diets, which produce ketones with a fruity or acetone smell
Nose, sinus and throat causes
- Tonsil stones: small whitish, foul-smelling lumps that form in pits of the tonsils.
- Chronic sinusitis and postnasal drip.
- Tonsillitis and throat infections.
- A foreign object in a child's nose, causing foul odor and one-sided discharge.
Stomach and whole-body causes
Bad breath from the stomach is less common than people think, because the esophagus is normally closed. However:
- Reflux can bring up sour-smelling contents.
- Diabetic ketoacidosis: fruity, acetone breath.
- Kidney failure: ammonia or urine-like breath.
- Liver failure: a musty, sweet smell (fetor hepaticus).
- Lung infections such as bronchiectasis or a lung abscess: foul sputum and breath.
- Bowel obstruction: rarely, a feces-like smell with vomiting.
What the smell can suggest
| Smell | Possible cause |
|---|---|
| Rotten egg, sulfur | Bacteria on tongue and gums |
| Fruity or nail polish | Ketones from fasting, keto diet or diabetic ketoacidosis |
| Ammonia or urine | Kidney failure |
| Musty, sweet | Liver disease |
| Sour | Reflux |
| Putrid, with sputum | Lung infection, bronchiectasis |
How doctors and dentists assess bad breath
A dentist checks for gum pockets, decay, tongue coating, dry mouth and tonsil stones, and may use a breath-measuring device. If the mouth is healthy, a primary care doctor or ENT specialist looks for nasal, sinus, throat, stomach and metabolic causes, with blood tests for blood sugar, kidney and liver function as needed.
How to get rid of bad breath
- Clean your tongue once or twice a day with a tongue scraper or brush, reaching as far back as is comfortable.
- Brush for 2 minutes twice a day with fluoride toothpaste.
- Clean between teeth daily with floss or interdental brushes.
- Clean dentures every night and leave them out overnight.
- Keep your mouth moist: drink water through the day and chew sugar-free gum to boost saliva.
- Use an antibacterial mouthwash containing cetylpyridinium chloride, chlorhexidine (short term) or zinc, after brushing. Alcohol-based mouthwashes can dry the mouth.
- Stop smoking.
- See a dentist every 6 to 12 months, or sooner for bleeding gums.
Mints and sprays only mask odor for a short time.
Frequently asked questions
Why do I have bad breath even though I brush my teeth?
Brushing teeth misses the back of the tongue, the spaces between teeth and gum pockets, which are where most odor comes from. Add tongue cleaning and daily flossing. If breath is still bad after two weeks, see a dentist to check for gum disease, decay, tonsil stones or dry mouth.
Can bad breath come from the stomach?
Occasionally. Reflux can cause sour breath, and burping brings up food smells. But most persistent bad breath comes from the mouth, even in people with stomach symptoms. Treating the mouth first is usually the most effective step.
What is the difference between bad breath and halitosis?
They mean the same thing. Halitosis is the medical term for persistent bad breath. Some doctors use halitosis for odor that persists despite good oral hygiene, and our page on halitosis covers that medical side in more detail.
Why is my breath bad in the morning?
Saliva flow drops during sleep, so bacteria multiply on the tongue and release sulfur gases. Mouth breathing and snoring make it worse. Morning breath clears after brushing, tongue cleaning and eating. It is normal unless it persists through the day.
Can a keto diet cause bad breath?
Yes. Very low-carbohydrate diets and fasting make the body burn fat and produce ketones, including acetone, which is exhaled and smells fruity or like nail polish. It usually fades after a few weeks as the body adapts. Drink water and keep up oral hygiene.
Sources
This guide was written from current patient and clinical guidance, including:
- American Dental Association: Bad breath (halitosis)
- NHS: Bad breath
- Mayo Clinic: Bad breath
- MedlinePlus: Breath odor
- National Institute of Dental and Craniofacial Research: Dry mouth