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What causes bad breath?

Bad breath...halitosis, whatever you call it, it’s something almost all of us suffer from at some point in our lives. So what causes this timeless turnoff, and what can you do about it?

Causes of bad breath

The odor is caused by wastes from bacteria in the mouth, the decay of food particles, other debris in your mouth and poor oral hygiene. The decay and debris produce a sulfur compound responsible for the unpleasant odor.

Bad breath also may occur in people who have a medical infection, diabetes, kidney failure or a liver malfunction. Dry mouth (xerostomia) and tobacco also contribute to this problem. Even stress, dieting, snoring, age and hormonal changes can have an effect on your breath. An odor that comes from the back of your tongue may also indicate postnasal drip.

To eliminate bad breath, you need to stop it at the source.

Infected Gums

This can be one of the most obvious causes of bad breath. To get gums back into shape, brush thoroughly and often with a soft-bristle brush, and get into the habit of regular flossing. Your dentist can advise you of the appropriate treatment for all dental problems.

Dirty teeth

“There are more animals living in the scum on a man's teeth than there are men in a whole kingdom,” said Anton van Leeuwenhoek, a 17th-century Dutch scientist known for his work on the microscope. Whether or not there is any truth in this, teeth can certainly collect their fair share of odor-producing debris. Best for keeping oral bacteria to a minimum is frequent brushing (with or without toothpaste) or even just swishing the mouth with water.

A foul tongue

Once you’ve given your teeth and gums a thorough cleaning, don’t forget about your tongue. Removing bacteria from the back of your tongue can go a long way in fighting bad breath, and the custom dates back to the Romans. Brush very gently, with a soft-bristle brush and keep away from the very back of your tongue as this may cause a gagging reaction.

An empty stomach

Yes, skipping meals can cause foul breath as it reduces the production of saliva needed to flush away bacteria from teeth, tongue and gums. Stress can also lead to a dry mouth, which can cause double trouble when coupled with the increase in stomach acid that stress can cause. Chewing gum and lozenges can step up saliva flow, as can between-meal snacks such as fresh fruits and vegetables.


You already know that smoking gives you cigarette breath. But did you know that tobacco causes dry mouth and destroys cavity-fighting antibodies in your saliva?

Overuse of mouthwashes

It may sound counterintuitive, but using too much mouthwash can actually worsen a bad breath problem by irritating oral tissue. For a quick fix, try a rinse made of water and a few drops of peppermint oil.

Last updated: October 2015

The oral health information on this website is intended for educational purposes only. You should always consult a licensed dentist or other qualified health care professional for any questions concerning your oral health.