It might seem that something like bad breath is bound to be a simple condition. After all, it’s just an odor in your mouth, right? But the truth is that bad breath is another manifestation of the complex interaction between your oral health and your overall health, and the reasons why you get bad breath can be simple and easy to fix, or they may be complicated and difficult to treat.

Here are 11 of the most common causes of chronic bad breath–not just bad breath related to the food you recently ate.

A woman holds her nose so that she doesn't have to smell others breath

Gum Disease

Gum disease is one of the most common causes of bad breath and also one of the most important. This is a common infection of the gums. The oral bacteria that thrive in these areas are usually anaerobic, which means they don’t breathe oxygen. Instead, they usually use sulfur in the way we use oxygen, so they excrete smelly sulfur compounds.

This makes bad breath a good warning sign that you should talk to your dentist about. It won’t just save your breath, it can save your life.

Infected Teeth

When you have an infected tooth, the infection can spread in your body and become life-threatening. Long before that point, though, you might notice the foul smell or taste of bacteria that are gathering in your infected tooth.

This is an especially important warning sign because when bacteria and their excretions are escaping into your mouth from your tooth, you’re less likely to experience the pain that most people use as a sign that it’s time to go to the dentist.

Tongue Bacteria

However, it’s also possible that bacteria are sheltering in a place that’s not especially harmful, just smelly. Your tongue is one of these places. If you’re not cleaning your tongue well enough, bacteria can build up there, causing foul smells or tastes.

Tonsil Stones

Your tonsils’ job is actually to catch bacteria. They are full of numerous small chambers known as “crypts” that trap bacteria, preventing them from getting deeper down your throat. But when your tonsils catch a lot of oral bacteria, as well as errant food particles, they can form into large deposits called tonsil stones. These can be very smelly.

It’s important to note that these large tonsil stones are often the side effect of excess bacteria somewhere else in your mouth, such as on your teeth, in your gums, or even in your tooth. That’s why recurring tonsil stones should motivate you to see the dentist.

Acid Reflux

Gastroesophageal reflux disease (GERD), or acid reflux, has gotten a lot of attention recently because we have come to understand that it can be a chronic condition, not just heartburn from eating spicy food. Along with acid, GERD can send undigested food up into your throat or mouth, both of which contribute to bad breath.

If you are experiencing other symptoms of GERD, such as regular heartburn, you should talk to your doctor.

Dry Mouth

Dry mouth is bad for your oral health. Your saliva is your body’s natural antibiotic. It regulates pH so your mouth doesn’t get too acidic. It also contains minerals that help your body rebuild your teeth. And it washes away food particles.

If you’re not producing enough saliva, you will likely have more oral bacteria and more food particles in your mouth, both of which contribute to bad breath. Dehydration can cause dry mouth. Heavy alcohol consumption can also contribute to dry mouth. Among its negative effects, smoking can dry out your mouth. Coffee can also reduce saliva production.

Successful treatment of dry mouth requires us to first identify why your body isn’t producing enough saliva. Lifestyle changes often make the difference. Otherwise, a dentist can recommend or prescribe saliva substitutes.

Retained Food

The food you eat shouldn’t stay in your mouth. You want to get it out of your mouth, but that doesn’t always happen. If you have cavities or gaps in your teeth, you can end up with retained food that sours in your mouth, causing a foul odor.

It’s a good idea to finish every meal with a glass of water to help clear your mouth of retained food (and stay hydrated so you don’t get dry mouth). But if you have cavities that are trapping food, reconstructive dentistry procedures like fillings are recommended, while orthodontics can help deal with gaps in your teeth.


What you eat can have a big impact on your breath, and we’re not talking just the liver and onions you had for lunch. Instead, your diet can actually change the way your body metabolizes food, which can contribute to a particular odor in your breath.

The most common cause of this is ketosis, which can be caused by going on a low-carb diet. It’s part of the point of the diet that your body breaks down more proteins. When you break down proteins, it produces a surplus of ketones, which can be smelled in your breath. It’s important to point out that one positive outcome is these low carb diets may help reduce the effects of migraines.

Health Conditions and Medications

Your overall health can also impact your breath. Some health conditions can literally be smelled on your breath. Diabetes is one of the most common, but some cancers can cause bad breath. A gluten sensitivity or allergy can also cause bad breath.

And the medications you’re taking can also contribute to your bad breath. Most often, it’s because your medication is causing dry mouth, a very common side effect of medications. But it could also be because the medicine is breaking down in your body and releasing chemicals with a certain smell.

Sleep Apnea, Snoring, and Chronic Morning Breath

Most of us get morning breath. That’s because your saliva production drops overnight, allowing the mouth to dry out and bacteria populations to grow. So in the morning your mouth smells a bit worse.

But if you have really bad breath in the morning, it could be related to snoring and sleep apnea. The cause of snoring and sleep apnea is an obstruction in your airway. Your body may try to compensate for this by breathing through your mouth, which can dry out the mouth. It can also increase your risk of tooth decay and gum disease.


Sometimes, people don’t actually have bad breath, but they are concerned that they do. The fear of bad breath is sometimes called “Halitophobia.” Breath that people think is bad, but actually isn’t is known as “pseudo-halitosis.” People with halitophobia can usually be reassured. In rare cases, they might need therapy or professional support.  Dentists can also provide an objective reassurance to help people with halitophobia overcome their uncertainty.

Treat Bad Breath at Its Source

If you are looking for truly effective bad breath treatment, you need to try to identify its source. That way, you can get effective, long-lasting relief for yourself and everyone close to you.

To learn what’s behind your bad breath in San Jose, please call (408) 354-5600 today for an appointment with dentist Nancy Nehawandian at Top Down Dental in Los Gatos.