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.

If you constantly feel like you have snot, mucous or phlegm dripping down from the back of your nose combined with a pretty bad case of rotten breath, you may well be suffering from a condition known as Post Nasal Drip.

Post Nasal Drip occurs when excess mucous is produced by your sinuses and accumulates at the back of your nose or throat.

The exact causes of Post Nasal Drip vary from person to person and include allergies, certain medications, colds and flu, pregnancy and other hormonal changes, smoking, rhinitis (i.e. inflammation of the nose or its mucous membrane) and sinusitis (i.e. inflammation of the sinuses).