Chances are, you already know the basics when it comes to keeping your breath minty-fresh (or at least non-offensive to those in whiffing distance). You brush, floss, and maybe do a quick rinse with mouthwash a few times a day. You wouldn't dream of ordering garlic bread on a first date, and you always pop a stick of sugar-free gum shortly after downing your morning coffee. But let's say you do all those things, yet your breath still stinks. (Check out these 12 crazy things your dentist knows about you just by looking in your mouth.)

That's the case more often than you might think, as poor oral hygiene is not the most common cause of bad breath, said Harold Katz, DDS, a dentist, bacteriologist, and founder of the California Breath Clinics. Most chronic bad breath is actually due to dry mouth: When you don't have enough moisture, the bacteria that live in your mouth thrive.

"When you sleep at night there's little or no saliva production. That's what causes dryness and morning breath," explained Katz.

If morning breath is your only issue, you don't really have a problem (just brush!). But many people have dry mouth (and the accompanying bad odor) that lingers all day, often thanks to a medication they're taking.

"Seventy-five percent of prescription drugs, including antidepressants, antihistamines, and blood pressure drugs, have dry mouth as a side effect," Katz said.

So if you find people frequently backing away when you're talking, ask your doc if your meds might be to blame. If so, sipping more water, chewing sugarless gum, or maybe switching to a different drug could help (as well as these 11 natural solutions for your bad breath). 

In other instances, chronic bad breath could signal that something is amiss elsewhere in your body. And—believe it or not—the specific scent may provide clues that can help your doctor or dentist figure out what's wrong.

If your breath smells like mothballs...

You might have allergies, post-nasal drip, or a sinus infection. When you have chronic sinus issues, the bacteria in your mouth can convert the proteins in mucus into a compound called skatole. Taking allergy medication, rinsing your sinuses with a neti pot, or (if your doctor determines you have a bacterial infection) starting antibiotics should help. (Discover how to heal 95+ health conditions naturally with Rodale's Eat for Extraordinary Health & Healing.)

If your breath smells fruity...

You might have diabetes. Sugar in your bloodstream normally heads into your cells, where it's used for energy. If that doesn't happen, blood sugar rises, and your cells start burning fat for energy. The byproduct of that process is ketones, which can make your breath smell fruity, said Dr. Shilpi Agarwal, a family medicine doctor and integrative medicine physician in Washington, DC.

"If I noticed that in a patient, I would test her blood sugar" to see if she's developed diabetes, Agarwal said. 

If your breath smells like sour milk...

You might be lactose intolerant. This odor might indicate that you're not breaking down the protein in dairy proteins properly, Katz said. Of course, you'll also likely have other symptoms, such as diarrhea, cramps, and gas after indulging in milk products (here are 9 essential tips for living with lactose intolerance).

If your breath smells like a dirty diaper...

You might have a tonsil stone. Bacteria and debris can get stuck in your tonsils and form a visible "stone" in the crevices. "It's really rotten, like a dirty diaper," says Agarwal, who says that your primary care doctor can probably remove the offending particle with a swab or forceps. 

MORE: "I Got Lung Cancer Even Though I Never Smoked"

If your breath smells like something's rotting...

You might have a lung disease. A very foul odor—"much worse than traditional bad breath," says Katz—could be a sign of a lung problem ranging from an infection (like pneumonia) to cancer. Interestingly, breath tests designed to identify the odors associated with cancer are currently in the works. If you suspect you might have any problem with your lungs, see your doctor for an exam. After listening with a stethoscope, she might refer you for blood work, a chest x-ray, or other tests. 

This article orginally appeared on Prevention.com.