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Pass the mints: let’s talk halitosis

A graphic showing to faces from the side. One is breathing out a foul-smelling greenish cloud that the other is smelling

We’ve all been there. You wake up after a big night out of eating and drinking and your mouth feels (and tastes) like the bottom of a parrot’s cage.

Probably smells like it, too. Congratulations, you officially have bad breath (halitosis).

But don’t feel too bad—it happens to almost everyone at some point. According to Harvard Medical School, about 30% of the population complains of some sort of bad breath.

Some people have a persistent and strong fear of having bad breath, known as halitophobia.

There is also a name for a condition where people worry excessively about having bad breath when they don’t—pseudo-halitosis.

Bad breath can be caused by a range of factors, some not even in or near the mouth, but the mouth is the most common source.

Oral hygiene

Bad breath is often caused by sulphur-producing bacteria that can live on the teeth, gums, the surface of the throat, mouth, and tongue. The bacteria break down food particles and the decaying food produces a bad smell.

Maintaining good oral hygiene by brushing twice a day and flossing once a day can help keep food particles and bacteria under control and limit bad breath. Don’t forget to brush your tongue—especially right at the back.

If you have dentures, mouth guards, or retainers, clean them every day. Drink sufficient water during the day and replace your toothbrush every 3-4 months. Get your teeth checked and cleaned at the dentist regularly.

A young woman with a white towel wrapped around her hair looks in the mirror as she brushes her teeth

Gum disease and tooth decay

Infections in the mouth, such as gum disease and tooth decay, can contribute to bad breath. Dental plaque is a sticky colourless film of bacteria, mucus, and food particles that forms on teeth and give them that ‘furry teeth’ feeling. The bacteria acting on the food particles produce acids that can destroy tooth enamel and cause gum disease.

If plaque is not removed from the teeth it can combine with minerals in your saliva and harden into a rough and porous deposit on the teeth or below the gumline called calculus or tartar. Both plaque and tartar can cause bad breath.

These build-ups also eventually cause gingivitis, or a gum infection.

If left untreated, gingivitis damages gum tissue and may turn into periodontal disease, which eats away at gum tissue and eventually bone, deepening and enlarging the pockets around the teeth.

Normally the gaps between your teeth and gums are about 1-3mm. Once they get deeper, a toothbrush and mouth rinses can’t quite reach them, so they need to be professionally cleaned or treated by a dentist or periodontist to heal them and stop them from getting worse.

As these pockets can hold food and bacteria, they also can produce bad odours.

A photograph of a basket containing garlic, brown and red onions, and spring onions

Smelly food and drinks

Your digestive system can absorb certain smelly compounds from strong smelling foods such as onions, garlic, and curries. Some of these can enter your blood stream and be excreted by your lungs, producing things such as garlic breath. Some drinks, such as coffee or tea, can give you breath odour.

A woman drinks a cool glass of water

Dry mouth

Some people have dry mouths. They may not produce enough saliva, smoke, sleep with their mouths open, or take medications that may cause a dry mouth.

Saliva helps to keep the mouth clean and reduces odour, so a dry mouth can mean bad breath.

If you have dry mouth, sipping water throughout the day can help. Special mouth moisturising products and saliva substitutes are available from your doctor and pharmacist. Limit your caffeine intake and don’t smoke or chew tobacco.

A hand reaches for a glass of red wine on a table, while the other hand holds a cigarette

Tobacco and alcohol

Smoking tobacco causes bad breath. It also dries your mouth, which makes it worse.  Excessive alcohol consumption can also dry out your mouth and cause bad breath, even though it’s a liquid.

Mouth, throat, lung, or sinus conditions

If you have a mouth, sinus, throat, or chest infection, you may develop bad breath. A post-nasal drip can also cause it.

Other diseases

Some diseases can cause unusual breath odours. For example, uncontrolled diabetes can cause the breath to smell fruity. Liver or kidney failure can cause it to smell fishy.

Sleep apnoea (when your breathing pauses or you breath shallow while sleeping) and gastroesophageal reflux disorder (GORD – where stomach contents enter and damage your oesophagus) can also cause bad breath.


If you’re worried about bad breath or it is persistent, you should seek medical advice. See your dentist first. They can smell your breath and see if you have a build-up of plaque or calculus or have signs of tooth decay or gum disease. Your teeth may just need a thorough clean.

If they think your teeth, gums, or mouth are not the cause, they may recommend visiting your GP to ensure you don’t have any underlying medical conditions.

More information

Last updated: 19 August 2022