Most adults have bad breath occasionally, particularly when their mouth dries out after, say, a full night's sleep or a long, dehydrating plane flight. About 25 percent of people worldwide, however, have chronic foul breath. Researchers around the world figured out years ago that gas-emitting bacteria on the tongue and below the gum line are largely responsible for rotten breath. But determining how best to eradicate these microbes' tenacious odors has been difficult.
Solutions to date offer only temporary relief. Even scrupulously skipping onions and garlic, swishing mouthwash after every meal, and brushing and flossing one's teeth until they gleam like pearls will probably not sweeten a case of stubbornly stinky breath. Lightly scraping away any coating on the tongue can greatly improve the fragrance of one's breath for at least a few hours. Certain bacteria-slaying mouthwashes provide short-term freshness, too, although many produce unpleasant side effects, such as a tingling sensation in the mouth. Lately some scientists have developed innovative mouth rinses that neutralize the rancid compounds produced by bacteria.
Recent evidence from international research suggests, however, that the most effective strategy for beating back bad breath may be more about nurturing helpful bacteria in the mouth than about destroying the offending germs and their by-products. Instead of singling out ostensible culprits, microbiologists are now shifting their focus to entire communities of microbes on the tongue, gum and teeth to figure out why some people have a sweeter-smelling oral village than others.