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Bad Breath (Halitosis)

Bad Breath (Halitosis)

Halitosis is the medical name for bad breath. It describes an unpleasant smell in the breath which is detectable by other people.

Bad breath is something we're probably all a little paranoid about. It's dead embarrassing and we all know we probably won't necessarily be aware of it ourselves, and our friends are likely to be too kind to mention it. So we find ourselves breathing into our cupped hands and having a sniff to check.

How will I know if I have it?

Unfortunately the breathing-into-your-hand technique may not work awfully well as we get used to our own odours so can't really smell them. Like the way that people with pets aren't aware their house reeks of cat or dog. Or the way you can't smell your own perfume on yourself. So you may have to rely on other people telling you. You could ask a close friend or family member if they have noticed anything. Or ask your dentist when you have your regular check-up. Your doctor would have a sniff for you if asked about it.

What is normal?

It's perfectly normal to have dog breath in the mornings. Your saliva stagnates in your mouth overnight, but once you are salivating again normally with breakfast, this improves. We all know our breath reeks after eating lots of garlic in particular, but also if lots of onions, spices or alcohol have gone down the hatch. Smokers tend to have an ashtray type of breath. But outside of these situations, if you have bad breath, there may be a problem causing it.

Read more about the symptom of bad breath, how common it is, and the types that exist.

What is the reason for bad breath?

Most of the time, it comes from a problem in your mouth. Which stands to reason, given that's the last place your breath came from. And it's usually down to a problem with your teeth and your oral hygiene regime. It may be due to gum or teeth problems, food particles festering between your teeth, or germs on your tongue. Occasionally it's from a problem at the back of your mouth in your tonsils. (Often parents are aware their kids have tonsillitis because of the way their breath stinks.)

Learn more about problems in the mouth which cause bad breath.

In some people it can come from other sources. Problems in the nose or reflux of acid from the stomach may cause bad breath. Some medicines may cause it, as may certain diets. Some illnesses can cause typical odours in the breath. Learn more about the causes of bad breath.

Will I need any tests?

Not usually. Your doctor or dentist may establish if your bad breath is coming from your nose or mouth, by asking you to breathe out of each in turn. A thorough dental examination will check for the majority of causes of bad breath, and then the dentist will be able to advise accordingly. Only if no cause is found will you need further tests. This might include a camera examination of your nose or gullet and stomach, or tests for acid reflux.

Read more about investigating bad breath.

How can I smell sweet again?

The most important way to sort out bad breath is to take a good look at your teeth-cleaning routines. It may be worth visiting your dental hygienist to get some advice. You should be cleaning your teeth for at least two minutes twice a day, ideally with an electric toothbrush. You should also clean your tongue each day. Clean between your teeth each day with dental floss or interdental brushes. Consider using a mouth wash once or twice a day.

If you smoke, consider quitting. Have a think about the things in your diet which might be making it worse. If there is a medical cause, such as acid reflux, your doctor should be able to help you with that.

Discover more about the treatment of bad breath.

How can I avoid having bad breath?

Good oral hygiene usually prevents bad breath. Essentially this just means brushing your teeth regularly and effectively. Stopping smoking, if you are a smoker, also helps.

Learn about good oral hygiene and preventing bad breath.

What is halitosis?

Bad breath (halitosis) means that you have an unpleasant smell on your breath that other people notice when you speak or breathe out.

How common is halitosis?

The exact number of people with bad breath is not known, but it is common. In some countries, studies have found as many as half of the population have problems with halitosis. In others the frequency is much less.

Types of halitosis

Halitosis can be:


Bad breath can be normal (physiological) in certain circumstances. This includes:

  • In the morning when you first wake up.
  • If you smoke.
  • After eating certain foods - for example, garlic, onions, spices, cabbage, sprouts, etc.
  • After drinking a lot of alcohol.
  • Fasting, being on a crash diet or a low-carbohydrate diet.


This means there is a problem causing it. This is usually a problem in the mouth, but it can be coming from other sources, or caused by a specific illness or condition.


In this case, the person doesn't actually have bad breath. Nobody else can smell it but the person becomes very anxious about it. An extreme version of this is called halitophobia, the fear of bad breath. Some people think they have bad breath when they do not, and nobody else can smell it. This can result in odd behaviour to try to minimise what they think of as their bad breath. For example, they may cover their mouth when talking, avoid or keep a distance from other people, or avoid social occasions. People with halitophobia often become fixated with teeth cleaning and tongue cleaning and frequently use chewing gums, mints, mouthwashes and sprays in the hope of reducing their distress. Treatment from a psychologist may help.

What are the causes of bad breath?

Coming from within the mouth

Most cases of bad breath (halitosis) come from germs (bacteria) or debris that build up within the mouth. This is discussed in more detail in its own section.

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:

  • Betel
  • Chloral hydrate
  • Nitrites and nitrates
  • Dimethyl sulfoxide
  • Disulfiram
  • Some chemotherapy medicines
  • Phenothiazines
  • Amfetamines
  • Lithium
  • 'Water' tablets (diuretics)
  • Bisphosphonates

Check the list of side-effects on the leaflet that comes with your medicine if you think it might be causing bad breath.


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. Low-carbohydrate diets also can cause this sort of bad breath.

Medical causes

Medical causes, other than problems in the mouth, are relatively uncommon. Possible causes include:

  • Nasal problems. For example, a lump (polyp) in the nose 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.
  • Sinus infections.
  • Throat infections such as tonsillitis.
  • Mouth infections, such as dental abscesses.
  • Infections or tumours of the lung.
  • Bronchiectasis.
  • Reflux of acid from the stomach ora stomach infection called Helicobacter pylori.
  • Diabetes
  • Severe kidney or liver problems.
  • 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.

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.

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.

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.

When to seek further help

If you have done everything you can in terms of the oral hygiene measures discussed in this leaflet and still have bad breath then see a doctor or dentist.

Who should I consult about bad breath?

You can see either a doctor or a dentist. Usually a dentist would be the first port of call, as they can do a thorough check of your teeth and gums, which are the most common source of the problem. If the dentist can't find a cause in your mouth, he or she may suggest you consult a doctor.

Will I need any investigations?

For most people this won't be necessary. You would have an examination of your mouth by your dentist. In some cases the dentist may suggest an X-ray to look further at your teeth. Your doctor may ask about other symptoms and examine you to look for other causes if the dentist cannot find a cause. If this is the case, you may need some tests to assess if you have a less common cause of bad breath. This might include:

  • Blood tests.
  • An examination of the inside of your nose with a tube (nasoendoscopy).
  • An examination of your gullet and stomach (gastroscopy).
  • A breath, blood or stool test for the germ Helicobacter pylori, which sometimes is a cause.

What is the treatment?

Good oral hygiene

For most people, the treatment for bad breath is much the same as the measures of good oral hygiene described in the prevention section. This means regular effective teeth-brushing and cleaning between teeth.

These routine daily procedures 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 may help 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.

Tongue cleaning

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. Some studies suggest that tongue scrapers or cleaners are slightly more effective than toothbrushes as a means of controlling halitosis.

Chewing gum

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.

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. Acidic 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 acidic 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.
  • When giving children medicines, such as Calpol®, use the sugar-free versions wherever possible.

Stop smoking

If you smoke, try to stop. Smoking increases the risk of developing gum disease.

If you have dentures and have bad breath

You may not be cleaning them properly. Ask your dentist for advice on cleaning dentures.

What treatment will I need if it isn't coming from my mouth?

This will naturally depend on the cause. For example, if it turns out you have nasal polyps, you might be prescribed a steroid nasal spray, or have an operation. If you have acid reflux, you may prescribed medicines such as proton pump inhibitors (PPIs) or ranitidine. You may be prescribed antibiotics if you have an infection, etc.

Good oral hygiene not only helps prevent halitosis, but also reduces the risk of us having cavities, abscesses, and gum diseases and losing our teeth.

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.

Teeth brushing

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 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 acidic 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. It may be that small interdental brushes are more effective, but studies have not yet shown this convincingly. 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.

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.

Further reading & references

  • Kapoor U, Sharma G, Juneja M, et al; Halitosis: Current concepts on etiology, diagnosis and management. Eur J Dent. 2016 Apr-Jun;10(2):292-300. doi: 10.4103/1305-7456.178294.
  • Halitosis; NICE CKS, November 2014 (UK access only)
  • Bollen CM, Beikler T; Halitosis: the multidisciplinary approach. Int J Oral Sci. 2012 Jun;4(2):55-63.
  • Yaacob M, Worthington HV, Deacon SA, et al; Powered versus manual toothbrushing for oral health. Cochrane Database Syst Rev. 2014 Jun 17;(6):CD002281. doi: 10.1002/14651858.CD002281.pub3.
  • Poklepovic T, Worthington HV, Johnson TM, et al; Interdental brushing for the prevention and control of periodontal diseases and dental caries in adults. Cochrane Database Syst Rev. 2013 Dec 18;(12):CD009857. doi: 10.1002/14651858.CD009857.pub2.
  • Kuo YW, Yen M, Fetzer S, et al; Toothbrushing versus toothbrushing plus tongue cleaning in reducing halitosis and tongue coating: a systematic review and meta-analysis. Nurs Res. 2013 Nov-Dec;62(6):422-9. doi: 10.1097/NNR.0b013e3182a53b3a.
  • Porter SR, Scully C; Oral malodour (halitosis). BMJ. 2006 Sep 23;333(7569):632-5.
  • Fedorowicz Z, Aljufairi H, Nasser M, et al; Mouthrinses for the treatment of halitosis. Cochrane Database Syst Rev. 2008 Oct 8;(4):CD006701.
  • Phillips IR, Shephard EA; Trimethylaminuria, University of Washington, 2007 (updated 2011)
  • Reidy JT, McHugh EE, Stassen LF; A review of the role of alcohol in the pathogenesis of oral cancer and the link between alcohol-containing mouthrinses and oral cancer. J Ir Dent Assoc. 2011 Aug-Sep;57(4):200-2.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.

Dr Mary Harding
Peer Reviewer:
Dr Helen Huins
Document ID:
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