© Sonja Pacho\Corbis(© Sonja Pacho\Corbis )

Wondering why your loved ones are giving you more personal space than you’ve asked for? Suspicious about the Altoids left on your desk with dental floss bows? If you’re one of 90 million Americans suffering from chronic bad breath, here are some of the possible causes, as well as remedies to restore your fresh breath—and relationships.

Top 5 Causes of Bad Breath

1. A dirty mouth

“Ninety percent of mouth odors come from mouth itself—either from the food you eat or bacteria that’s already there,” says Dr. Richard H. Price spokesman for American Dental Association. “Mouth odor is like any other body odor—the result of microbes living in the body giving off byproducts.” In the mouth, this means bacteria that normally live in the mouth interact with food particles, blood, tissue, etc., to create volatile (i.e., stinky) sulfur compounds. If you don’t clean properly, the bacteria build up, and next thing you know—that’s not toothpaste on your tongue.

2. A mouth out of balance

Certain mouth conditions can exacerbate bacterial growth and odor, such as gum disease and dry mouth. Gum disease causes bloody gums, creating more elements for those pesky bacteria to putrefy. But it is a dry mouth that is the more common cause of bad breath. Saliva helps flush out the mouth, keeping bacteria moving so they don’t settle down and multiply, while drier mouth is a breeding ground for bacteria. In spring and summer, allergy medications can dry you out; in winter, dry heat tends to be the culprit.

3. Stinky foods

If it stinks going in, chances are it’s going to stink coming out. The obvious offenders are onions, garlic, alcohol and tobacco. And foods don’t only create a stench in the mouth. “Plant oils are absorbed and the byproducts enter your bloodstream so you are actually breathing the odors out via your lungs three to four hours later,” says Jeannie Moloo, a registered dietitian and spokeswoman for the American Dietetic Association. [Fulldisclosure: Moloo is the author’s cousin.]

4. Not enough carbs

You look great after four weeks on Atkins, so how come you still can’t get a date? High-protein, low-carb diets cause your body to burn stored fats for fuel instead of carbs and can lead to a condition called ketosis. “As fat burns, ketones build up in the body, and some are released through breath,”explains Moloo. “Unfortunately ketones don’t smell particularly good.” And bad breath trumps six-pack abs.

5. Illness

Occasionally, bad breath can be a sign of a more serious illness. The most common systemic causes of bad breath are diabetes or GERD (or gastro esophageal reflux disease). Diabetes can also cause ketosis, and the resulting bad breath is sometimes one of first symptoms that lead to diagnosis. GERD is a backflow of acid from the stomach to the esophagus. Less common but possible are liver or kidney disease—when toxins from these organs are excreted through the lungs, causing bad breath.