Stare at yourself in the mirror and bring your tongue out – do you have a white coating on your tongue and bad breath? A lot of people who experience bad breath (halitosis) have a noticeable white coating at the end of the tongue. Even if you don’t notice anything, you might have a coating, at times referred to as a biofilm, on your tongue formed by countless unusual microbes, the leftovers of food and body cells, and a non-cellular medium that holds it in unison.

You wonder about it. You worry that you have it but that no one is telling you about it. So you discreetly cup your hand over your mouth, exhale, and take a quick whiff. Smells okay. But still you wonder: “Do I have bad breath?”

This fear of foulness may help explain why Americans spend $1 billion a year on mouthwashes and other breath-freshening products. Most cases of bad breath result from bacteria that live in the mouth, according to William Replogle, Ph.D., professor of family medicine at the University of Mississippi Medical Center in Jackson. As these microbes feed on food residues, they produce foul-smelling compounds that make your breath offensive. They also produce irritating toxins that cause your gums to pull away from your teeth, forming pockets that harbor even more bacteria. And the more bacteria that live in your mouth, the worse your breath becomes.