In most cases of persistent bad breath (halitosis), the smell comes from a build-up of germs (bacteria) within the mouth. These are in food debris, in plaque and gum disease, or in a coating on the back of the tongue. Good oral hygiene will often solve the problem. That is, regular teeth brushing, cleaning between the teeth, cleaning the tongue, and mouthwashes. Other causes of persistent bad breath are uncommon.
What is bad breath?
Bad breath (halitosis), means that you have an unpleasant smell on your breath that other people notice when you speak or breathe out. The exact number of people with bad breath is not known, but it is common.
How can I tell if I have bad breath?
A main problem with bad breath (halitosis) is that often the only person not to notice it is the person affected. (You become used to your own smell and do not tend to notice your own bad breath.) Often, the only way to know about it is if a person comments on it. However, most people are too polite to comment on another person’s bad breath. You may have to rely on a family member or a close friend to be honest and tell you if you have bad breath.
Perhaps you could ask your dentist next time you have a check-up. A dentist will normally be able to say if you have bad breath. Gum disease is a common cause of bad breath and a dentist will be able to advise on treatment if you have gum disease.
Some people suggest a simple test which you can do yourself to detect bad breath. Lick the inside of your wrist. Wait a few seconds for the saliva to dry. Then smell the licked part of the wrist. If you detect an unpleasant smell, you are likely to have bad breath.
What are the causes and types of bad breath?
Coming from within the mouth
Most cases of bad breath (halitosis) come from germs (bacteria) or debris that builds up within the mouth. This is discussed in more detail later in the leaflet.
Morning bad breath
Most people have some degree of bad breath after a night’s sleep. This is normal and occurs because the mouth tends to get dry and stagnate overnight. This usually clears when the flow of saliva increases soon after starting to eat breakfast.
Dry mouth (xerostomia)
Bad breath associated with a dry mouth is caused by a reduction in the cleansing mechanism of the mouth as a result of reduced flow of saliva. There are many causes of a dry mouth. The most common cause is after a night’s sleep (discussed above). Dry mouth may also occur:
- Due to a lack of fluid in the body (dehydration).
- As a side-effect of some medicines (for example, tricyclic antidepressants).
- As a symptom of some diseases (such as Sjögren’s syndrome).
- Following radiotherapy to the head and neck region.
Foods, drinks and medicines
Chemicals in foods can get into the bloodstream, and then be breathed out from the lungs. Most people are familiar with the smell of garlic, spicy foods and alcoholic drinks on the breath of people who have recently eaten or drunk these. Various other foods and medicines can cause a smell on the breath. This type of bad breath is temporary and easily cured by not eating the food. (However, some people eat spiced food every day. As a result, they will constantly have a typical smell on their breath.)
If a medicine is causing the problem then discuss possible alternatives with your doctor. Medicines that have been associated with bad breath include:
- Chloral hydrate
- Nitrites and nitrates
- Dimethyl sulfoxide
- Some chemotherapy medicines
Most non-smokers can tell if a person is a smoker by their breath which “smells like an ashtray”. Stopping smoking is the only cure for this type of bad breath. Smoking also increases the risk of developing gum disease – another cause of bad breath.
Crash dieting or fasting
Can cause a sickly sweet smell on the breath. This is due to chemicals called ketones being made by the breakdown of fat. Some ketones are then breathed out with each breath.
Other medical causes are uncommon. Some people with nasal problems can get bad breath. For example, a lump (polyp) in the nose, sinusitis or a small object stuck in a nostril (occurs most commonly in children) can cause a bad smell. In this situation, the smell tends to occur only, or more severely, when you breathe out through your nose. It is not so noticeable when you breathe out through your mouth. Infections or tumours of the lung, throat, mouth or tonsils are sometimes a cause. Other causes are rare.
However, in these medical cases, there are usually other symptoms that would indicate the cause. For example, a blocked nose, sinus pain, chest symptoms, a high temperature (fever), etc. If you are otherwise well and have no other symptoms apart from bad breath, the smell is likely to be coming from a build-up of bacteria in the mouth and other medical causes are unlikely.
Fish odour syndrome (trimethylaminuria)
This is a rare medical cause but worth being aware of. It typically causes breath and body odour that is often like a fishy smell. It occurs because the body loses the ability to properly break down trimethylamine which is found in certain foods. There is then a build-up of trimethylamine in the body which is released in sweat, urine, and breath. Urine and blood tests can help to confirm this diagnosis if it is suspected.
Bad breath coming from within the mouth
In most people who have bad breath (halitosis), the bad smell is thought to come from germs (bacteria) and debris within the mouth. As the bacteria break down proteins and other debris in the mouth, they release foul-smelling gases. One or more of the following may contribute to the build-up of bacteria, debris and bad breath:
- Food stuck between teeth. Normal teeth brushing may not clear bits of food which can get stuck between teeth. The food then rots and becomes riddled with bacteria. Regular cleaning between the teeth can clear and prevent this problem.
- Plaque, tartar (calculus) and gum disease. Dental plaque is a soft whitish deposit that forms on the surface of teeth. It forms when bacteria combine with food and saliva. Plaque contains many types of bacteria. Calculus is hardened calcified plaque. It sticks firmly to teeth. Gum disease means infection or inflammation of the tissues that surround the teeth. If your gums look inflamed, or regularly bleed when you clean your teeth, you are likely to have gum disease. The severity can range from mild to severe.
- Coating on the back of the tongue. In some people, a coating develops on the back part of the tongue. It is not clear why this occurs. It may be from mucus that drips down from the back of the nose (postnasal drip). The coating can contain many bacteria. This explains why bad breath can sometimes occur in people with otherwise good oral hygiene.
- Tonsil stones (tonsilloliths). These are clusters of calcified material that form in the tonsillar crypts, or crevices of the tonsils. They are made up mostly of calcium but can contain other ingredients such as magnesium and phosphorus, and can feel like a small lump in the tonsils. Rarely harmful, they can be a nuisance and hard to remove and can often cause bad breath.
Routine oral hygiene – recommended for everyone
The main treatment of bad breath coming from within the mouth is good oral hygiene. Aim to get into a regular habit of good oral hygiene – in particular, teeth brushing and cleaning between teeth.
Brush your teeth at least twice a day. Use a soft-tufted brush and a toothpaste that contains fluoride. The head of the brush should be small enough to get into all the areas of the mouth. Spend at least two minutes brushing, covering all areas (the inside, outside, and biting areas of each tooth). Pay particular attention to where the teeth meet the gum. Get a new toothbrush every 3-4 months. Studies suggest that powered toothbrushes with a rotation-oscillation action (where the brush rapidly changes direction of rotation) remove plaque and debris better than manual brushes.
Ideally, brush your teeth either just before eating, or at least an hour after eating. The reason for this is to help prevent tooth erosion. Many foods contain acids. In particular, fizzy drinks (including fizzy water) and fruit juices. After your teeth are exposed to acid, the enamel is a little softened. But, the action of calcium and other mineral salts in the saliva can help to counteract and reverse this softening. Therefore, do not brush teeth immediately after eating when the enamel tends to be at its softest. In particular, after eating or drinking acid foods and drinks. It is best to wait at least an hour after eating or drinking anything before brushing.
Cleaning between teeth
Clean between your teeth after brushing once a day, but ideally twice a day. This is to remove plaque from between teeth. Dental floss is commonly used to do this. However, some studies suggest that small interdental brushes may do a better job than floss. The aim is to clean the sides of the teeth where a toothbrush cannot reach. Also, to clear the spaces between teeth (the interdental spaces) of debris. Some people who have not cleaned between their teeth before are surprised as to how much extra debris and food particles can be removed by doing this in addition to brushing.
If you are not sure how to clean between your teeth, then ask your dentist or dental hygienist. Briefly: normal floss looks a bit like cotton thread. Cut off about 40 cm. Wind the ends round your middle fingers of each hand. Then grab the floss between the thumbs and first finger to obtain a tight 3-4 cm section which you can pull between teeth. Gently scrape the floss against the sides of each tooth from the gum outwards. Use a fresh piece of floss each time.
Some people prefer floss tape which slides between teeth more easily than normal floss. Also, some people use disposable plastic forks with a small length of floss between the two prongs. These may be easier to hold and manipulate. However, they are expensive. Some people use sticks, or small interdental brushes to clean the space between the teeth.
The gums may bleed a little when you start to clean between your teeth. This should settle in a few days. If it persists, see a dentist, as regular bleeding may indicate gum disease.
Food and drink
Sugars and sugary foods in the mouth are the main foods that germs (bacteria) thrive on to make acid which can contribute to tooth decay. Acid foods and drinks are also a main factor in tooth erosion. So, some tips:
- Limit the amount of sugary foods and drinks that you have. In particular, don’t snack on sugary foods.
- Try to reduce the amount of acid in contact with your teeth. So, limit fizzy drinks (including fizzy water) and fruit juices, as these tend to be acidic. Perhaps just limit yourself to one fizzy or fruit juice drink a day. Otherwise, choose drinks that are much less acidic, such as still water, and milk, tea, or coffee (without sugar).
- Drink any acid drinks, such as fizzy drinks and fruit juices, quickly – don’t swish them around your mouth or hold them in your mouth for any period of time.
- Brush your teeth at least an hour after eating or drinking anything – especially acidic foods and drinks. (See above for reasons.)
- Likewise, do not brush your teeth within an hour of being sick (vomiting), as stomach acid will be part of the vomit.
Other general tips
Other things which are important to keep your teeth and gums healthy are:
- If you smoke, try to stop. Smoking increases the risk of developing gum disease.
- If children need medicines, wherever possible use sugar-free medicines.
- Have regular dental checks at intervals recommended by your dentist (normally at least once a year). A dentist can detect build-up of plaque and remove tartar (calculus). Early gum disease can be detected and treated to prevent it from getting worse.
Other things you can do if you have bad breath
The measures above are usually sufficient to look after your teeth and to prevent bad breath. However, if you still have bad breath coming from your mouth then the following extra measures will usually cure the problem.
Consider using a mouthwash each day. Chemicals in the mouthwash aim to kill germs (bacteria) and/or neutralise any chemicals that cause bad breath. It is difficult to advise on which mouthwash is the most effective. A number of clinical trials have shown that various ingredients are good at reducing bad breath. These include chlorhexidine, cetylpyridinium chloride, chlorine dioxide, zinc chloride and triclosan. The various mouthwashes that you can buy usually contain one or more of these ingredients, plus various other ingredients.
Note: some people are reluctant to use a chlorhexidine-containing mouthwash long-term. This is because it has an unpleasant taste, can give rise to a burning sensation in the mouth if used too frequently, and can cause (reversible) staining of the teeth or occasionally some temporary darkening of the tongue. Also, some mouthwashes contain alcohol as one of their ingredients. There is some concern that long-term use of alcohol-containing mouthwashes may be a risk factor in the development of mouth cancer. Also, young children should not use a mouthwash if they may swallow it.
Consider cleaning the back of your tongue each day. Some people do this with a soft toothbrush dipped in mouthwash (not toothpaste). An easier and better way is to buy a special plastic tongue scraper from a pharmacy. You need to place it as far back as you can and then gently scrape forward to clear the tongue of any coating. A review in 2006 (cited at the end) concluded that … “tongue scrapers or cleaners are slightly more effective than toothbrushes as a means of controlling halitosis in adults”.
Some people chew sugar-free gum after each meal. It is not clear how well gum helps to reduce bad breath but chewing gum increases the flow of saliva. Saliva helps to flush the mouth to help clear any debris remaining from the meal.
If you have dentures and have bad breath
You may not be cleaning them properly. Ask your dentist for advice on cleaning dentures.