17 Reasons Why Your Breath Smells Bad

• Having bad breath is kind of like getting toilet paper stuck to the bottom of your foot: usually harmless, but so awkward that nobody will tell you about it. At the microbial level, bad breath happens when the naturally occurring bacteria in our mouths break down the food particles that are lingering in between our teeth, along our gum lines, and, especially, on our tongue. This process releases a bunch of stinky compounds and gives rise to the dreaded bad breath—or, as it's more formally called, halitosis.
• The good news: It's is usually temporary. The bad news? It's often caused by a less-than-stellar brushing and flossing routine—as well as a bunch of other foods and habits too. Here are 17 reasons why your breath smells bad.

RELATED: 3 Drinks That Will Make Your Breath Reek

Obviously, right? Yep, morning breath is pretty much a given, but here's why it happens: While you're sleeping peacefully, the bacteria in your mouth are anything but. The bugs take advantage of the fact that your production of saliva slows way down during sleep—and since your saliva helps "clean" your mouth, your breath might have a bad odor until you brush your teeth the next morning. Morning breath is totally normal, but some researchers refer to it as "morning halitosis."

RELATED: 6 Easy Steps to Becoming a Morning Person

Mouth-breathing may make your saliva evaporate, which can dry out your mouth and reduce your mouth's ability to rinse away food particles. Some people breathe through their mouths while they sleep, but many people often do it during exercise as well, says Hadie Rifai, a dentist at the Cleveland Clinic . (In fact, dental hygiene in athletes is currently being studied by experts: One 2015 study by researchers from Germany found that the more time people spent in training, the more likely they were to have cavities. The scientists also speculated that the reduced saliva flow during exercise may play a role.) That's not a reason to stop exercising, of course. Just make sure you stay hydrated during a workout and replenish your fluids afterwards, Dr. Rifai says.

RELATED: Why Your Breath Might Start to Smell Worse as You Get Older

Garlic and onions are two famous offenders, but other culprits include spices, cabbage, Brussels sprouts, cauliflower, and radishes. And even though the pungent scent of those foods might fade away after an hour or two, it can still come back up again—in one big garlicy burp. And bad breath from food can occasionally stem from the GI tract, not just your mouth. When you digest food, the chemicals are eventually absorbed into your bloodstream and enter your lungs, where you can expel them later, "says John Grbic, a dentist at ColumbiaDoctors in New York City.

RELATED: How to Get Rid of Garlic Breath

Skipping meals is a surefire way to have bad breath. That's because when we don't eat, we don't produce as much saliva. Why's that important? Because saliva doesn't just clean up food particles, it also breaks down that food to help it slide down our throats more easily, says Dr. Grbic. (Oh, and one more thing: Skipping meals isn't a very good way to lose weight, either.)

RELATED: What Is the OMAD Diet? Everything You Need to Know About This Extreme Intermittent Fasting Weight-Loss Plan

Add halitosis to the list of health conditions that can be caused by cigarettes. Unsurprisingly, smoking not only increases the amount of odor-producing compounds in a person's mouth and lungs, but the habit can also dry out your mouth, leading to lower saliva production, according to a 2004 review by researchers from Hong Kong.

RELATED: How to Keep Your Smile Pretty and Healthy

RELATED: Black Hairy Tongue Is a Legitimate Condition–but It's Not as Scary as It Looks

The mucus in your nose helps filter all the foreign particles that you breathe in from the environment—a good thing. But what happens when that mucus starts building up in the back of your throat because you have terrible pollen allergies or a nasty cold? Those foreign particles eventually travel into your mouth, settle on the surface of your tongue, and in turn trigger bad breath, according to one 2012 review in the International Journal of Oral Science. As if a sore throat wasn't bad enough.

RELATED: 8 Ways to Get Rid of Post-Nasal Drip

People who slash their carbohydrate intake have been known to report increased levels of halitosis. And, in fact, when researchers from Yeshiva University compared subjects on a very low-carb diet to those on a low-fat diet, they found that more people in the former group reported having bad breath than the latter. Though, it should also be noted, the low-fat dieters also confessed to more burping and, um, farting.)

RELATED: Keto Breath Is a Common Problem for Low-Carb Dieters—Here’s What You Can Do About It

Your mom has already warned you that a buildup of plaque can erode your teeth, leaving you with cavities. And while poor oral hygiene certainly contributes to bad breath, those "holes" may also trigger halitosis indirectly, too : "Food can get caught in the cavities," explains Dr. Grbic, and since cavities can be hard to clean, the remnants of your last meal can linger there for longer-than-usual periods of time, which can then lead to more bad breath. (For the record, yes, you'll need a filling.)

RELATED: 9 Things Your Dentist Can Tell About Your Health By Looking in Your Mouth

We're not just talking about braces—orthodontic appliances like dentures and fixed bridges can be difficult to maintain too. But it's important that you clean them every day, says Dr. Grbic, as they're also prime magnets for food particles, which can become lodged in the material. (Research also shows that dental appliances are linked with higher amounts of plaque accumulation—which is why a good cleaning regimen is so important.)

RELATED: Gum Health Basics: What to Look Out For and How to Prevent Trouble

Alcohol lingers on your breath long past last call. In fact, one 2007 study by researchers from Israel found that drinking alcohol was linked to increased rates of halitosis—and this, despite the fact that their subjects had fasted for 12 hours overnight and were also allowed to brush their teeth in the morning. The study authors suspect that not only does booze dry out a person's mouth, but that a certain odor is triggered when the body metabolizes alcohol.

RELATED: How to Get a Younger-Looking Smile

The overwhelming majority of halitosis cases are caused by the bacteria in a person's mouth—but researchers also suspect that in a minority of people, bad breath is triggered by a GI disorder like gastroesophageal reflux disease (GERD), in which the contents of a person's stomach leak back up into the esophagus. One 2007 study published in the journal Oral Diseases found that bad breath was more prevalent in people with GERD than those with other digestion problems, possibly because the disease may damage a person's throat tissue.

RELATED: 11 Foods That Help Heartburn, According to Gastroenterologists

Strep is a bacterial infection, not a viral one, and those invading bugs can cause your bad breath to smell bad, says Dr. Grbic. Not only that, but other kinds of sinus infections can turn into bacterial ones that produce a smelly, pus-like type of mucus. (Sorry for the visual.) Plus, some of these infections are also associated with specific types of bacteria that are known to produce a particularly bad odor in a person's mouth.

RELATED: 7 Signs You Could Have Strep Throat

Here's the thing: Your partner might wake up in the morning smelling like half-a-bottle of Listerine, while you might eat an onion ring and have to cover your mouth for the next 30 minutes. And in some cases, that might not have anything to do with how often either of you brush your teeth. Everyone has their own saliva composition and different kinds and levels of oral bacteria, all of which affect how your breath will smell in certain situations, says Dr. Rifai.

RELATED: This Electric Toothbrush Has a Game-Changing Feature—and It's on Sale

You probably don't need to worry about this one unless you have type 1 diabetes; it's pretty rare. But if your breath develops a sweet, almost sugary scent to it, that's a sign that you might be experiencing diabetic ketoacidosis, a life-threating condition for people with diabetes (usually type 1) that could cause a heart attack or kidney failure. Other symptoms include frequent urination, nausea, and muscle stiffness. Dr. Grbic says that dentists almost always see this in patients with undiagnosed diabetes. It's often a sign that their blood sugar levels are dangerously high and they need medical help right away, he says.

RELATED: 12 Healthy Ways to Lower Your Blood Sugar

Sjogren's syndrome (SS) is a disorder of the immune system, and it tends to show up in middle-aged women and those with other autoimmune conditions like rheumatoid arthritis and lupus. (That said, even young, otherwise healthy people can develop SS—Venus Williams was diagnosed in 2011.) People with SS often have a very dry mouth , which—you guessed it—increases their risk of halitosis.

RELATED: This Drastic Diet Change Helped Venus Williams Fight Her Autoimmune Condition

Up to 1% of people may have a disorder called halitophobia—a false belief that they have bad breath. It's a serious condition, and one that be extremely debilitating. To be clear: We're not talking about just a lingering suspicion of bad breath—we mean a persistent fear of it. People with halitophobia become absolutely convinced that their halitosis is driving other people away, even after a dentist has confirmed that they don't have the condition. Unfortunately, this phobia isn't well-studied, but if you suspect that you might have it, it's important to seek psychological help from a counselor or a specialist.

RELATED: I Tried the Waterpik Toothbrush Flosser, and Now I Love Water Flossing

To get our top stories delivered to your inbox, sign up for the Healthy Living newsletter