Bad breath (halitosis)

by | First Aid and Self-Care, Symptoms

Halitosis is the medical term for bad breath – breath that smells unpleasant to others. Most people have had bad breath at one time or another. It is especially common first thing in the morning (morning breath) or whenever you wake after a sleep, and doesn’t necessarily mean anything is wrong with you. However, in some people bad breath is a sign of a problem that needs medical or dental attention.

How can you tell if you have bad breath?

It can be hard to know if you have halitosis, because it’s difficult to judge whether your own breath smells normal or not. You can try breathing out through your mouth into your cupped hands and immediately breathing in through your nose, or licking the outside of your hand or wrist, waiting a few seconds, then smelling where you licked.

A close friend or relative may be able to judge far more accurately than you can whether your breath is bad or not. However, most people don’t like to comment on other people’s breath, in case they seem rude.

It is possible to believe you have halitosis, even when your breath actually smells normal. This is a kind of mental health issue called halitophobia.

If you are concerned about your breath, it may be best to ask your dentist or doctor to assess you for halitosis. Although it may feel awkward asking the question, getting a professional opinion and finding out what you can do about the problem may help you feel better.

What causes bad breath?

There are quite a few different causes of bad breath, ranging from simple oral hygiene issues, to health conditions that need medical or dental attention. Some causes are transient (passing relatively quickly), while others are ongoing.

Causes of transient (temporary) bad breath

Lots of people experience bad breath from time to time, which they find passes after a little while. Common causes of transient bad breath include:

  • smoking
  • drinking alcohol
  • eating certain foods – such as those high in garlic, onion or spices
  • sleeping – saliva helps keep your mouth clean and when you sleep you produce less saliva, so you can get bad breath after sleeping (especially if you breathe through your mouth – mouth breathing – rather than your nose).

Causes inside the mouth

In many cases of bad breath, the cause is a problem inside the mouth. Such problems include:

  • trapped food – when tiny bits of food are trapped in the teeth, gums and tongue, they are broken down by bacteria that produce foul-smelling chemicals, especially ‘volatile sulphur compounds’ (VSCs) like hydrogen sulphide
  • gum disease (periodontal disease) – caused when a sticky film of bacteria (plaque) builds up between your teeth and gums
  • mouth infections – unhealed wounds, tooth cavities (caries), abscesses, and other sores in the mouth like ulcers
  • salivary gland problems – if your salivary glands don’t produce enough saliva, this can cause a dry mouth (xerostomia), which can cause bad breath.

While most bad breath is caused by problems inside the mouth, it is possible to have bad breath caused by a problem in another part of the body.

Such problems include:

  • ongoing infections in the nose or throat 
  • ongoing tonsillitis or tonsil stones (small lumps of bacteria and debris that form on the tonsils)
  • sinusitis, or post-nasal drip (the drainage of mucus secretions from the nose or sinuses down the back of the throat)
  • infections of the lungs and airways
  • gastroesophageal reflux disease (GORD)
  • severe kidney disease causing uraemia (a build-up of wastes that are normally removed by the kidney in the blood)
  • hepatic encephalopathy (a condition when the liver is unable to remove toxins from the blood).

Other causes

Bad breath may also be caused by:

  • fasting – this can lead to ketoacidosis, a condition that develops when fat in the body breaks down and releases chemicals called ketones
  • medications – some medicines when they break down in the body release chemicals that cause your breath to smell; others can cause a dry mouth (xerostomia).

Most halitosis originates in the mouth. The usual cause is the breakdown of food particles by bacteria. This process of breakdown is exactly the same as the process that causes food to ‘go off’. This is known as putrefaction. Most people’s mouths contain large numbers of bacteria, especially in dental plaque, the substance that builds up on, and between, teeth that are not cleaned regularly. The crevices in the surface of the tongue can also contain odour-causing bacteria.

What makes bad breath worse?

Anything that increases the number of odour-producing bacteria in the mouth can make halitosis worse.  For example:

  • not cleaning your teeth daily – this includes flossing as well as brushing
  • wearing dentures that don’t fit properly or aren’t cleaned regularly
  • allowing your mouth to get dry – this can happen if you don’t drink enough water, or you breathe through your mouth instead of your nose (‘mouth-breathing’).

Sometimes foods that contain certain oils, such as garlic, onions and spices, will produce bad breath, but only on a temporary basis until the food is eliminated from your body. Dieters may have bad breath because of changes in their metabolism.

Some bad breath originates in the nose, throat and respiratory passages. For example, sinus infections, postnasal drip and respiratory infections can lead to bad breat

Smokers, and those taking certain drugs, may have bad breath. Sometimes, people with diseases of the liver or kidney, complications of diabetes or digestive problems have unpleasant breath as a result, but this is not common.

Diagnosing bad breath

To diagnose halitosis, your doctor will take a history to determine whether there may be causes within your mouth, or whether there are symptoms of a condition elsewhere in the body which may be contributing to your bad breath. It is important to discuss all medications you are taking even those bought over the counter or herbal reparations. The doctor will then take a look in your mouth and may do a simple smell test that involves comparing the odour of the breath that comes out of your mouth with the breath that comes out of your nose. If bad breath is coming only from your mouth, this suggests that the cause is probably inside the mouth, while bad breath coming only from your nose suggests the cause may be inside the nose or sinuses. If bad breath is coming from both your nose and mouth, the cause may be further inside the body (see above).


Treatment for halitosis depends on the cause. In some cases, improving your oral hygiene – brushing and flossing more regularly, for example – is all that needs to be done. However, if you have a problem with your teeth or gums, you may need to see a dentist.

As well as professionally cleaning your teeth, dentists can provide any necessary dental treatment, such as a filling if there is tooth decay. They can also advise you on things you can do yourself at home, like use toothpastes or mouthwashes designed to kill bacteria in the mouth.

If you have had your mouth checked by a dentist and find you still have persistent bad breath, see your doctor. Depending on the suspected cause, they may refer you to a specialist who can further investigate the issue.

How do you prevent bad breath?

There are some simple things you can do to help prevent halitosis.

  • Brush your teeth and tongue thoroughly at least twice a day, using a soft-bristled toothbrush and a fluoride-containing toothpaste, paying particular attention to the areas where the teeth meet the gums. This prevents plaque building up and removes the tiny food particles that would otherwise collect in the mouth and start to smell.
  • Clean between your teeth at least once a day, using dental floss or a small interdental brush (available from chemists and supermarkets). This helps remove plaque from places where your toothbrush can’t reach. You can also use a tongue scraper to clean the back of the tongue.
  • If you wear dentures or other dental appliances, make sure you clean these thoroughly every day.
  • Avoid eating too many sugary foods and drinks, which encourage bacterial growth in the mouth, and are also a cause of tooth erosion.
  • Stop your mouth from getting too dry by drinking plenty of water and chewing healthy foods like carrots and apples that encourage your saliva to flow.
  • See a dentist regularly to help prevent problems with your teeth and gums.
  • If you are a smoker, consider quitting. Not only does it make your breath smell bad, it also stains your teeth and makes you more likely to get gum disease.

Although some mouthwashes (such as those containing chlorhexidine) may help with bad breath on an occasional or short-term basis, they can cause problems if used long-term, such as staining your teeth and fillings, and are no substitute for good dental hygiene.