85 to 90% of bad breath (halitosis) is caused by oral bacteria. Some bad breath has medical causes, which is why, if you have halitosis, it's a good idea to first check with a doctor. But for the vast majority of people with bad breath, bacteria are the culprit.

Bacteria in order to live, must consume food. And, along with that, they excrete wastes.

When bacteria live in your mouth, the food they eat is the food you eat. When food remains in the mouth for an extended period, they eat quite a bit. If you brush right after eating, and if you confine your eating to mealtimes, you'll greatly reduce their food intake and will fight bad breath.

The waste produced by many oral bacteria consists of sulfur compounds. Sulfur compounds are notoriously smelly (hydrogen sulfide is the notorious "rotten egg" smell). So it's fairly easy to see that oral bacteria are the culprit.

A list of the smelly sulfur compounds excreted as waste products by the bacteria that live in your mouth:

• Hydrogen sulfide is one waste product of oral bacteria.
• Another is methyl mercaptan, which is the stinky odor emanating from barnyards and feed lots.
• Another oral bacteria waste product is dimethyl sulfide, which is also associated with brackish ocean water.

These bacterial waste products are called "volatile sulfur compounds," or VSCs. The word volatile means that they easily turn into gasses, which, of course, is required for us to smell them.

There are some other bacterial waste products besides volatile sulfur compounds that contribute to odor. Here is a list of some of them:

• Putrescine -produced by decaying meat.
• Skatole - present in human feces.
• Isovaleric Acid - produced by sweaty feet.
• Cadaverine - the compound responsible for the smell of corpses.

Everyone has traces of these compounds in their breath. Usually the amounts are low enough so they aren't detected. But, as levels of these compounds rise, they can definitely become obnoxious.

Of the list above, putrescine, methyl mercaptan, hydrogen sulfide, and skatole are waste products of anaerobic bacteria. These bacteria prefer environments that have little or no oxygen. Too much oxygen may kill these bacteria.

It isn't practical or desirable to eliminate all the bacteria that grow in your mouth. Many of them are beneficial. What's important is that you keep a healthy balance of bacteria and minimize the numbers of odor-causing bacteria.

To minimize these bacteria, you can minimize anaerobic conditions in your mouth. Plaque, the thin, bacteria-laden film that grows on your teeth and also on your tongue, can protect the underlying bacteria from oxygen. The more plaque buildup you have, the more favorable environment your mouth is going to provide for these odor-causing bacteria. Oxygen, in this case, is a helpful disinfectant. Keep your mouth clean, and you permit oxygen to reach all the surfaces where bacteria can live and keep anaerobic, odor-causing bacteria to a minimum.

What foods promote bad breath?

The sulfur-containing compounds excreted by odor-causing bacteria are generally waste products of bacteria that are digesting proteins. Thus, as you consume high-protein foods, you are helping to create bad breath. Especially as you neglect to brush and floss, you help feed these bacteria for extended periods and thus will aggravate the odor in your mouth.

High protein foods that tend to lead to halitosis:

• Meat
• Seafood
• Eggs
• Dairy foods
• Nuts
• Peas and beans
• Cereal grains

High-protein foods have become more popular recently because of weight-control diets such as the Atkins Diet and the South Beach Diet. Maybe the most sensible policy is to eat a normal, balanced diet, with adequate amounts of protein, carbohydrates, fats and oils.

Where do bad breath bacteria live?

These bacteria can live anywhere in your mouth. But their favorite environment is the tongue, with its deep crevices and papillae, especially the back of the tongue, which is somewhat protected. The crevices around and between the teeth also provide a protected area. So cleaning your tongue and the crevices around your teeth is an important aid to cure bad breath. If you have a tartar buildup, this also provides a hiding place for bacteria. This needs to be removed professionally.

Do you have bad breath? You're so close to it and you're probably used to the smell. Get an honest friend or perhaps a dental professional to answer the question for you.

This information is provided for you by the mynewsmile.com cosmetic dentist referral service, and was personally written by Dr. David Hall. If you would like to be referred to a cosmetic dentist who would be expert in all of these questions about tooth bleaching, please see our cosmetic dentist referral page.

This web site's original launch date: Dec. 2, 1995