Frequently Asked Questions (FAQ) on Bad Breath


What causes bad breath?

The common causes of bad breath (also known as halitosis) include:

  • Oral conditions
  • Food
  • Smoking
  • Medical Conditions

Oral conditions

The most common cause of bad breath arise from oral conditions, as the breakdown products of some oral bacteria produce a number of sulphide-type gases which has a bad egg sort of smell. These foul-smelling gases are termed volatile sulphur compounds (VSC). The oral bacteria are continually producing VSC, but this only becomes a social problem when the quantity of oral bacteria producing VSC is allowed to flourish. This may occur when there is:

  • Dry mouth (xerostomia). Saliva is our natural antiseptic mouthwash. It washes out food debris as well as dilutes and neutralizes any bacterial waste products. When the mouth is dry, food debris tends to remain and oral bacteria tends to flourish, hence greater VSCs are produced. You may find you have bad breath only when you wake up in the morning. This is because when you sleep, saliva flow decreases and your mouth becomes dryer, which results in a temporary rise in VSC. As your saliva flow goes back to normal, it disappears. Some of the more common causes of dry mouth are:
    • Side effect of drugs such as antihistamines
    • Mouth breathing
    • Radiotherapy for head and neck cancers - where the salivary glands are irradiated, salivary flow is greatly reduced
    • Alcoholism
  • Furry tongue - The tongue is probably the primary source of bad breath in both healthy individuals and those with gum disease. The rough surface of the tongue harbours bacteria that produces VSC, particularly if very furry.
  • Food debris
  • Tooth decay (dental caries or cavities)
  • Periodontal (gum) disease
  • Mouth ulcers
  • Oral cancers
  • Dentures - like our natural teeth, artificial teeth that are not kept clean can also harbour oral bacteria that produce VSC


Typically garlic and onion. After the food digests and gets into the bloodstream, their pungent oils are exhaled through the lungs, producing its characteristic smell. This is a transient problem (for about a day) that solves itself as the food passes through the digestive system.


Cigarette, cigar and pipe smoking also cause a stale"smokers" breathe from the accumulation of nicotine, tar etc. from the tobacco smoke onto both the teeth and the soft tissues of the mouth.

Medical Conditions

This includes medical conditions of the nose (such as sinusitis, post-nasal drip), throat, digestive system, kidney, liver, diabetes. Even fasting can cause bad breath!

How do I tell if I have bad breath?

Trying to confirm it by breathing out into your cupped hands and breathing in your exhaled air unfortunately does not work, as the air from forced exhalation and speaking is different, and usually your nose gets used to your own smells!

What's that stink?

Bad breath is usually most obvious when you are speaking to someone in close proximity. If you notice that people try to keep a distance from you when you speak, you may have bad breath.

So the most reliable (next to purchasing a bad breath meter usually used for research) is to ask someone you are close to (in relationship) for their frank opinion..... Children are usually good - they're innocently honest!

But if you prefer the privacy of a self-test, use a spoon to scrape the surface of tongue right at the back, where it looks white and furry, because this is where VSC-producing bacteria like to make their home (Warning: This may make you retch!)

Scrape back of tongue with a spoon

Leave it to dry for a few seconds then smell it. That's how others smell you! This test however, is only useful if the cause for your bad breath is the bacteria living in the back of your tongue.

Will mouthwashes prevent bad breath?

General use mouthwashes are helpful for masking bad breath, however, they will not prevent it unless the cause for bad breath is identified and corrected.

Specially formulated mouthwashes to eradicate VSC-producing bacteria that make the back of the tongue their home can prevent bad breath only if this is the cause of your bad breath.

How do I get rid of bad breath?

If your bad breath is only temporary, for example, only when you wake-up in the morning, this is because of dry mouth in the night as the saliva flow diminishes, causing a temporary accumulation of VSC. However, if longer term, then what needs to be done to get rid of bad breath depends on its cause:

Cause Remedy
Dry mouth

Drink water throughout the day. Avoid alcohol, as alcohol itself can cause dry mouth.

If drug-induced, see your doctor to discuss if other drugs without this side-effect can be substituted. In addition, for permanent dry mouth because of radiation treatment, the use of artificial saliva substitutes or oral hydrating gels can be useful. In Singapore, Biotene, has a range of useful products.

Food debris See your dentists to see if food traps can be eliminated. Modify brushing to increase effectiveness. Special brushes, for example, interspace brush can be used to remove trapped food for spaces to prevent food stagnating.
Caries See your dentists to get the cavities restored, or the tooth removed if unrestorable.
Periodontal See your dentists for appropriate treatment.
Dentures See your dentists for appropriate treatment.
Furry tongue Pro biotic lozenges to change your oral bacteria (see below).
Clean the back of the tongue with a tongue scraper or a brush.
Medical condition See your doctor for management of the medical condition.

Recent studies indicate that individuals with a specific bacteria, streptococcus salivarius (Kazor et al. 2003) seem not to have bad breath. It is thought that streptococcus salivarius competes with the bacteria that produce VSC that cause bad breath, keeping them from proliferating. Therefore, if the bacterial population in the mouth of people with bad breath can be altered to allow streptococcus salivarius to predominate rather than the VSC producing bacteria, bad breath can be eliminated. This pro biotic approach of adding "good" bacteria to eliminate the "bad" bacteria in the mouth seems to hold promise (Burton et al. 2006). Ask your dentist if he stocks these pro biotic lozenges.