Bad Breath (Halitosis): Causes and How to Get Rid of It

Bad breath, known medically as halitosis, affects around 1 in 4 people, and roughly 85% of it starts in the mouth rather than the stomach. The smell comes from volatile sulphur compounds (VSCs) released by bacteria, most of them living on the back of the tongue. This guide explains the real causes, split into oral and non-oral, how to test your own breath when you cannot smell it yourself, the home remedies that actually work, and when persistent bad breath signals a problem that needs a dentist or doctor. It also covers how failing old dental work causes odour and where to get treatment for bad breath in Istanbul, Turkey.

The information in this article is for educational purposes only and does not constitute medical advice. Consult a qualified dental professional before making any treatment decisions.

What causes bad breath?

Bad breath is caused mostly by bacteria in the mouth that break down food and tissue proteins and release smelly volatile sulphur compounds. Around 85% of all halitosis originates in the oral cavity, while the rest comes from the airways, stomach or a wider health condition, as set out in a review in the International Journal of Oral Science (Bollen & Beikler, 2012). Knowing which group applies decides whether a dentist or a doctor solves the problem.

The 3 main sulphur gases behind the smell are hydrogen sulphide (a rotten-egg odour), methyl mercaptan (a smell like old cabbage), and dimethyl sulphide. Anaerobic bacteria produce these gases fastest where oxygen is low, which is why the coated back of the tongue and deep gum pockets are the main sources.

What are the oral causes of bad breath?

The oral causes of bad breath centre on the tongue, the gums, and trapped food, which together explain most cases. A coated tongue holds the largest reservoir of odour-producing bacteria, so a tongue that looks white or yellow is often the real culprit. Untreated gum disease is the next most common cause, and professional periodontal treatment removes the bacteria deep in the gum pockets that brushing cannot reach.

• Tongue coating on the back of the tongue
• Gum disease (gingivitis and periodontitis)
• Dry mouth from low saliva, mouth breathing or medication
• Food trapped between teeth or around old fillings
• Tooth decay and failing crowns, veneers or dentures

What are the non-oral causes of bad breath?

The non-oral causes of bad breath sit outside the mouth and account for roughly 15% of cases. These need medical rather than dental attention, because better brushing will not change them. The most common non-oral causes are listed below.

• Acid reflux (GERD) and other digestive issues
• Sinus infections, post-nasal drip, and tonsil stones
• Uncontrolled diabetes, which can give a sweet or fruity smell
• Low-carbohydrate or fasting diets that produce acetone, “keto breath.”
• Kidney or liver disease, and some prescription medicines

How do you know if you have bad breath?

You cannot reliably smell your own breath because the brain tunes out a constant smell through a process called olfactory habituation. This is why many people either worry needlessly or miss a real problem, so an objective check matters more than a sniff. Use one of the 3 simple self-tests below, or ask a dentist who can measure sulphur gases in parts per billion with a device called a Halimeter.

• Lick the back of your wrist, let it dry for 10 seconds, then smell it
• Scrape the back of your tongue with a spoon and smell the residue
• Smell your floss after cleaning between the back teeth

What are the different types of bad breath?

Bad breath falls into 3 distinct types, and telling them apart prevents both over-treatment and missed disease. Most cases are harmless and temporary, but a small group reflects a genuine ongoing problem and another reflects no problem at all. This distinction is rarely explained in standard advice, yet it changes what you should do next.

Type	What it means	What to do
Transient	Normal morning breath or odour after garlic, onion or coffee	Nothing; it clears with eating, drinking and cleaning
Persistent (genuine)	Odour that stays despite good oral hygiene	Find the cause with a dentist, then a doctor if the mouth is healthy
Halitophobia (pseudo-halitosis)	A strong belief in bad breath that objective tests do not confirm	Reassurance and, if needed, psychological support rather than dental treatment

How do you get rid of bad breath?

You get rid of bad breath by lowering the bacterial load in the mouth and keeping saliva flowing, which resolves most cases at home. Because the tongue holds most of the odour bacteria, cleaning it is often the single most effective step. The following 6 measures target the real sources of the smell:

• Brushing twice daily and cleaning between the teeth once a day
• Scraping the back of the tongue gently with a tongue scraper
• Drinking water throughout the day to keep the mouth from drying out
• Chewing sugar-free gum to stimulate saliva after meals
• Booking a professional dental cleaning, usually every 6 months
• Stopping smoking, which both dries the mouth and adds its own odour

One caution that most guides skip: alcohol-based mouthwashes can dry the mouth and make breath worse over time, and any mouthwash masks odour rather than treating its cause. Choose an alcohol-free antibacterial rinse, and treat it as a support to cleaning, not a substitute for it.

When should you see a dentist or doctor for bad breath?

You should see a dentist for bad breath when it persists for more than 2 to 3 weeks despite good oral hygiene and tongue cleaning. A dentist checks for gum disease, decay, dry mouth and failing dental work, which between them explain most stubborn cases. If your mouth is healthy and the odour continues, the next step is a doctor, because the cause may be reflux, a sinus condition or a wider health issue.

How is persistent bad breath treated professionally?

Persistent bad breath is treated professionally by finding and removing the source rather than masking the smell. A professional dental cleaning clears the plaque and tartar that feed odour bacteria, and gum treatment addresses the deep pockets where they thrive. Where old dental work is to blame, the long-term fix is to repair or replace it, which is covered next.

Can old veneers, crowns or dentures cause bad breath?

Old veneers, crowns or dentures can cause bad breath when worn edges, gaps or a poor fit trap food and bacteria against the gum. Poorly fitted porcelain veneers or ageing dentures create sheltered spaces that brushing cannot clean, so the odour returns no matter how carefully you brush. Renewing or refitting the restoration removes the trap and usually resolves the smell.

Where can you get treatment for bad breath in Istanbul, Turkey?

You can get treatment for bad breath in Istanbul, Turkey at a clinic that diagnoses the cause and offers cleaning, gum treatment and restoration renewal in one place. Maltepe Dental Clinic supports international patients through a structured dental tourism process, from the first online assessment to aftercare once you return home. Patients travelling for dental treatment abroad typically save 50% to 70% compared with equivalent UK private costs, which makes combining a breath assessment with wider treatment practical in a single trip.

Frequently asked questions about bad breath

Bad breath raises a few recurring questions, answered briefly below.

Why does my breath smell even after brushing?

Your breath smells even after brushing because most odour bacteria live on the back of the tongue and in gum pockets that a toothbrush misses. Adding tongue scraping and treating gum disease targets these hidden sources. If the smell continues with a healthy mouth, the cause may lie outside the mouth.

Can mouthwash cure bad breath?

Mouthwash cannot cure bad breath on its own because it masks the odour rather than removing its source. An alcohol-free antibacterial rinse helps as a support, but cleaning the tongue, teeth and gums does the real work. Alcohol-based rinses can even dry the mouth and worsen the smell.

Why does a low-carb or keto diet cause bad breath?

A low-carb or keto diet causes bad breath because the body burns fat and releases ketones such as acetone, which leave the body through the lungs. This “keto breath” has a fruity or metallic smell and does not come from mouth bacteria. Drinking more water and adjusting carbohydrate intake reduces it.

Why do I have bad breath that seems to come from my throat?

Bad breath that seems to come from the throat is often caused by tonsil stones, small lumps of calcified debris trapped in the tonsils. They release sulphur gases and can persist despite good oral hygiene. Gargling dislodges small stones, while recurrent cases may need an ENT assessment.

Can a dentist tell where bad breath comes from?

A dentist can usually tell where bad breath comes from by examining the tongue, gums and teeth and, in some clinics, measuring sulphur gases with a Halimeter. This identifies whether the cause is oral or whether you should see a doctor. Pinpointing the source is the step that makes treatment work.

Sources

• Bollen, C.M., & Beikler, T. (2012). Halitosis: the multidisciplinary approach. International Journal of Oral Science, 4(2), 55–63. https://doi.org/10.1038/ijos.2012.39
• NHS. (2024). Bad breath. NHS.uk. https://www.nhs.uk/conditions/bad-breath/
• Cleveland Clinic. (2023). Halitosis (Bad Breath). my.clevelandclinic.org. https://my.clevelandclinic.org/health/diseases/17771-bad-breath-halitosis
• American Dental Association. (2023). Bad Breath (Halitosis). MouthHealthy.org. https://www.mouthhealthy.org/all-topics-a-z/bad-breath-halitosis