This might explain why Americans are doling out over $3 billion to buy gum, mints and other industry remedies in pursuit of fresh breath. Chronic bad breath, a condition known as halitosis, can stem from poor oral hygiene, dry mouth and even the Atkins diet.

Below, Richard H. Price, DMD, a consumer adviser for the American Dental Association who practiced dentistry in Newton, Mass., explains the best ways to combat bad breath, and not just disguise it.

What causes bad breath?
Ninety percent of bad breath problems are caused by unique bacteria in the mouth. They are anaerobic bacteria that produce volatile sulfur compounds that consist of hydrogen sulfides and mercaptans. These compounds are what gives bad breath its distinctive odor, that rotten egg odor.

How does what you eat affect your breath?
There's food and there's diet, and both can influence your breath. There's onion breath, garlic breath, tobacco breath. The odor-causing chemicals that give onion, for example, its distinctive odor are digested and the digested products go into the bloodstream. The blood is brought back to the lungs to get fresh oxygen, so you breathe in and out the onion breath (or garlic breath, or tobacco breath).

There's also bad breath that is associated with certain diets, such as the Atkins diet. In order to efficiently burn fat, you need a certain amount of carbohydrate, and the Atkins diet is a low carbohydrate diet. So if you don't have enough carbohydrate, the body has to modify the way it deals with fat and it produces a chemical substance known as ketones. Ketones give the breath a different odor.

How does poor dental hygiene contribute to bad breath?

Even somebody whose mouth is meticulously scraped, cleaned and flossed can still have bad breath, but if you don't have good oral hygiene, you're more likely to have it. With poor dental hygiene, we're talking about a buildup of plaque. Plaque is made up of colonies of bacteria mixed with mucous, cells that slough off the cheeks, and food debris. Food sitting around anywhere else is called garbage — and garbage has a distinct aroma to it. So decomposing foods that are not removed from the mouth via dental floss, a toothbrush, and rinsing, will produce odors.

In addition, a mouth that has unfilled cavities or gum disease in which there might be spaces between the tooth and gums, gives bacteria a place to hide where you can't clean them out. In fact, people who experience bleeding of the gums from gum disease have breakdown products in the blood that give the mouth a distinctive odor.

How do dry mouth conditions contribute to bad breath?
For the most part, if the bacterial population is kept under control, the volatile sulfur compounds that these bacteria produce dissolve in saliva. It's when saliva gets saturated that the smelly vapors will start to come out. You've seen a quickly moving stream in the woods. It's much cleaner than the ones that are stagnant. Well, with a copious saliva flow, you tend to clean the mouth out a lot. When the mouth is dry, there's not as much cleansing action.

Respiratory infections and allergies can contribute to dry mouth. People with colds and allergies tend to breathe through their mouth, which dries out the mouth. And if you get a postnasal drip, the mucous dripping coats the back part of the tongue. Beneath this mucous coating are these anaerobic bacteria and, to them, that's Club Med. So they just start flourishing.

Do underlying medical problems cause bad breath?
I said 90 percent of the problems occur in the mouth, which leaves 10 percent for somewhere else. There could be infected sinuses, diabetes due to the production of ketones, gastrointestinal conditions such as bowel obstruction and certain lung conditions. My job as a dentist is to figure out if it's coming from the mouth and treat it. If it's not coming from the mouth, then I refer somebody to a medical doctor.

How do you treat bad breath?
There's ways of treating it and keeping these bacterial populations under control. If you want to cure under-arm odor or foot odor, what do you do? You take a shower, which reduces the bacterial population. So for bad breath, you brush, floss and keep your mouth as clean as possible.

But even the healthiest mouth can have the bad breath problem because the bacteria tend to accumulate in the back part of the tongue. If you scrape your tongue once in the morning and once at night, most of us can defeat bad breath. Anything that cleans the tongue, as far as I'm concerned, can act a tongue scraper. A toothbrush is good, but the problem with a toothbrush is it has a certain amount of height, where the top of the brush is and the bristles end. For some people, it'll bang into the roof of the mouth. You should be able to find a tongue scraper on the shelf of your local drugstore.

Remember to keep the mouth moist. Some people also use a saline nasal spray if they have postnasal drip. Also make sure that you're drinking water and have a piece of fruit, which adds fiber, which stimulate saliva flow and adds some abrasiveness to the food to help clean off plaque.

Does gum or candy help?
The answer to that is yes and no. You can stimulate saliva flow after a meal chewing gum or during the day. But if you're using it as a crutch, what you're doing is replacing one odor with another. If the gum or candy is sugar-laden, you might have problems with cavities. If there are sugar substitutes in the candy or gum, you might wind up with digestive problems because a lot of people have a gastric response to the substitute sugars.

But certainly a Binaca blast may give you that extra confidence before meeting the woman or man of your dreams I guess.

Do mouthwashes help?
For the most part, mouthwashes replace one smell with another. You've got to treat the problem. But there's no question that it may help you through the tight spots.

What are common mistakes people make when they're brushing and flossing?
One of the more valuable things you can have on your sink is a three-minute egg timer. And brush and floss 'til the cows come home. I think one of the other misconceptions people have is that the toothbrush is going to do it all. You need special attachments to vacuum your house, to get in the nooks and crannies. You need special attachments, such as dental floss, to get to all parts of the mouth.

Another misconception people have is that all toothbrushes are the same. You want to choose a toothbrush that fits comfortably in your hand and in your mouth. You got a little mouth, use a little-headed toothbrush; I don't care if it says "kid" on it. You don't want a hard-bristled brush; all you need is something soft enough to brush the plaque away.

You do want to start with a toothpaste, a toothbrush and floss that carry the seal of the American Dental Association on the package. That way, you know the product was designed to treat you in the best manner without causing harm.