Bad breath, also known as halitosis, can be a major point of embarrassment for many people. The Academy of General Dentistry estimates that more than 80 million people experience chronic halitosis, but it’s often fixable once an underlying reason has been identified.
Chronic breath bad can offer clues to your overall health. So, before you chalk it down to poor oral hygiene or the nature of your eating habits, you might want to dig a little deeper into what could be triggering your halitosis. While the occasional bad breath is nothing to be concerned about, chronic foul-smelling breath may be a sign that something is amiss with your health (via Mayo Clinic). Taking some time to get it checked out may not only improve your social interactions, but it could also save your life. Here are some things your bad breath might be telling you about the state of your health.
You have digestive issues
There are many different ways that your gut may be the culprit behind your bad breath. Gastroesophageal reflux disease (GERD) is the number one gastrointestinal-related cause of mouth odor, gastroenterologist Randall Meisner told Health Beat. When the muscle between the esophagus and stomach doesn’t close properly, excess stomach acids travel back into the esophagus — the “food pipe” connecting the throat and stomach (via MedlinePlus). Since partially-digested foods are unable to pass through the digestive system, they can start to decay and emit a sour odor (via Healthline).
Bad breath might also stem from bacterial overgrowth in the small intestine, according to Health Beat. This occurs in people with diabetes or those who’ve had intestinal surgery. The good news is that a course of antibiotics often clears this up pretty quickly. More rarely, a person with bad breath may have a bowel obstruction, which is a fairly dangerous medical condition that involves something blocking the flow of waste in the large or small intestines (via Healthline). Similar to GERD, a blockage means that any food you eat gets trapped inside the digestive tracts and begins to ferment, which can result in breath that smells a bit like feces.
Another digestive health issue that could lead to halitosis is H. pylori infection, per a 2008 study in the Journal of Medical Microbiology. This is a type of stomach bacteria that causes peptic ulcers, and more severely, can increase the risk of gastric cancer.
You’re on a low-carb diet
Anyone who’s flirted with the Atkins, South Beach, or the keto diet is likely to have discovered the undesirable side effect of “keto breath” (via Verywell Fit). This tends to be somewhat different from ordinary bad breath. Some people describe it as a sweet, fruity smell, akin to rotting apples; others describe it as having a resiny aroma (like nail polish).
While keto breath can vary, it essentially stems from the effects of protein and fat metabolism, explained Verywell Fit. When people adhere to a low-carb diet, the body enters a metabolic state called ketosis, whereby natural chemicals known as “ketones” are released during the breakdown of protein and fat. This can lead to excessive accumulation of ketones inside the body, which is responsible for unpleasant-smelling breath.
A 2024 study identified another contributing factor of keto breath, namely the production of ammonia. When the body suddenly switches from processing carbs to mostly digesting protein, it ups the amount of ammonia in stomach gases and urine.
“If you have a metabolic cause of bad breath, there is very little the dentist can do; you have to change your diet,” periodontist Lawrence Simon told WebMD. The good news is that keto breath is temporary, explained Healthline. Most people notice a change in their breath within a few days or a week of starting a low-carb diet. The smell generally subsides as the body adjusts to consuming fewer carbs.
You have an infection
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Another possible source of halitosis is an abscess or infection in the mouth, throat, or lungs (via Healthline). This can make your breath smell like rotting tissue. For example, bronchiectasis — a chronic condition where the bronchial tubes (airways of the lungs) become abnormally widened and thickened — can lead to a build-up of mucus and triggers frequent respiratory infections that cause a rotten, fetid smell.
Chronic tonsillitis, namely a persistent infection of the tonsils, often results in the formation of pus-filled pockets around the tonsils (via MedicineNet). The stones (tonsilloliths) themselves contain sulfa, which, when crushed, exude that rotten-egg smell that many of us are familiar with. What’s more, tonsillitis is caused by excess bacteria that can give off a sulfur-like odor as it colonizes in the back of the mouth, noted Healthline.
Research also pinpoints bad breath as a common symptom of sinus infections. Sinusitis is inflammation or swelling of the nasal passages, which is brought on by viruses, fungi, allergies, or an autoimmune reaction, explained Medical News Today. It typically contributes to bad breath due to the infected mucus that runs from the sinuses into the back of the throat, where it meets with the air you breathe and exhale.
You’re not cleaning your teeth properly
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Poor oral hygiene tops the list of reasons for your bad breath, according to research published in the Journal of Natural Science, Biology and Medicine. When people don’t brush and floss regularly, decaying food debris accumulates on the teeth and tongue, causing bacterial plaque to build on the teeth (via Mayo Clinic). If this isn’t brushed away, over time it turns into hard tartar or calculus and collects even more bacteria, eventually forming plaque-filled pockets around the gums, also known as periodontitis, per Healthline. The inflammation that arises from periodontal diseases like gingivitis and periodontitis produces odorous compounds, the journal continued.
Food particles can also get trapped in dentures, crowns, and orthodontic devices that don’t fit snugly (via Mayo Clinic). And when these aren’t cleaned properly, odor-causing bacteria and plaque are likely to increase over time. Your tongue also traps bacteria that contribute to oral malodor. Practicing good oral hygiene can help prevent disease-causing bacteria from cultivating, such as brushing your teeth and tongue, using dental floss and mouthwash, and drinking lots of water.
You have a cavity
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Cavities are small holes that form in the teeth from the buildup of bacteria that erodes the enamel (via Colgate). Some 30% of American adults suffer from untreated dental cavities, as reported by the Centers for Disease Control and Prevention. While cavities don’t directly cause smelly breath, the bacteria that get stuck inside of them can start to smell like decay over time, making it harder for you to keep your mouth clean, notes the American Dental Association (ADA).
If left untreated, a cavity in the tooth can develop into an abscess, which is when the tooth is filled with pus and other infected material (via Healthline). This typically causes swelling and pain and produces a funk in the mouth, but it can also destroy your tooth. More severely, the infection can spread from the tooth’s center into the bones around the teeth and eventually pass into the bloodstream, resulting in potentially dangerous health complications.
You’ve been exercising outdoors too much
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Your outdoor workouts might be a slightly less predictable source of your bad breath. A study published by the European Respiratory Society found that athletes have a higher chance of developing breathing problems compared to the average person (via Reader’s Digest). About 10% of people who exercised outdoors experienced some kind of breathing difficulty, such as asthma, wheezing, or dry mouth. It was hypothesized that exercising outdoors can lead to nasal drainage, allergies, and chronic dry mouth — a symptom of which may be unfortunate breath.
During periods of intense aerobic exercise, people breathe more air into their lungs than when they’re not active and tend to inhale more deeply, Edward R. Laskowski, a professor at the Mayo Clinic’s department of physical medicine, told WebMD. They also breathe mostly through their mouths rather than the nasal passages, which have little hairs inside to help filter out harmful pollutants and particles in the atmosphere so that it doesn’t get into the lungs.
You need to change your diet
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Your bad breath might signify that you’ve been going a bit too heavy on the sugary treats. Some experts suggest a high-sugar diet contributes to halitosis by driving up the blood glucose levels in your saliva (via Insider). This creates a pretty cozy habitat for bacteria to feast and multiply, causing the smell of your breath to deteriorate over time.
Sugar can also take a toll on the condition of your teeth (via Mayo Clinic). As highlighted, the bacteria that are left behind by sugar create plaque, which only adds to the problem of smelly breath if left untreated. The World Health Organization cites sugar consumption as a prominent risk factor for cavities, recommending that people reduce their sugar intake to less than 10% of their daily caloric intake.
Additionally, a 2024 study in Microbiome highlighted the relationship between excessive alcohol consumption (more than three drinks per day) and poor oral health. The researchers analyzed the oral microbiome composition of spit samples from more than 1,000 healthy adult volunteers. They found that people who drank more alcohol had higher levels of bad bacteria in their saliva — a major consequence of which was dental caries, gum disease, and bad breath. Aside from negatively impacting your oral microbiota, the study’s authors noted that drinking too much can contribute to other health predicaments that underlie bad breath.
You have an enzyme disorder
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An enzyme disorder often goes under the radar but it could help explain your off-smelling breath. Digestive enzymes naturally occur in your body to help metabolize what you eat, but sometimes your body lacks or isn’t able to produce enough of a certain type of enzyme, which can cause unfortunate odor on the breath (via Healthline).
Trimethylaminuria is a genetic metabolic disorder whereby your body lacks the enzymes to properly break down trimethylamine — an organic compound that’s produced from the precursors of trimethylamine N-oxide and choline by the bacteria in your stomach, according to the National Organization for Rare Disorders. So when the body’s natural metabolic process doesn’t work as it’s meant to, there’s an accumulation of trimethylamine in the body. This is then excreted in bodily fluids such as your urine, sweat, and breath, resulting in a distinct odor that some would describe as rotten fish. Due to its association with halitosis and other bodily odors, trimethylaminuria sufferers can experience some serious social difficulties, which can spiral into other problems such as isolation and depression, according to a report in Clinical Biochemist Reviews.
You smoke cigarettes
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Bad breath is often considered one of the hallmarks of being a smoker. A 2024 study revealed that tobacco is a surefire contributor to unfortunate mouth odor, as approximately 80% of smokers have halitosis. Not only does smoking, in and of itself, cause what’s known as smoker’s breath, it can also engender tooth decay and gum diseases, exacerbating the problem of bad breath. Gum disease occurs when bacteria sneak under the gums and lingers on your teeth, resulting in plaque and tartar (via Healthline). In its early stages, this is known as gingivitis. Over time, it can lead to your gums receding away from the teeth, and creating pockets that are filled with odor-emitting bacteria.
Smoking also causes dryness of the mouth, which fuels bad breath, per Healthline. Saliva plays an important role in our oral hygiene, serving as a natural mouth rinse that washes down the cigarette smell and food particles that might otherwise hang around and become bothersome. For this reason, it’s important to drink plenty of water — or better yet, ditch the cigarettes all together to combat halitosis.
You’re dehydrated
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Dehydration decreases saliva production in the body (via Healthline). Not only does our saliva have antibacterial properties, but it washes away the debris of food particles that get caught in our teeth and gums. If these remain in the mouth, they start to rot and also trigger bacteria overgrowth that’s responsible for that foul-smelling sulfur stench you may start to notice over time.
Dry mouth is an ideal environment for bacteria to fester, which can kickstart a number of oral infections such as gum disease and cavities. Dry mouth tends to occur while we’re sleeping due to dehydration, and it can worsen when people sleep with their mouths open — hence, the funky “morning breath” most of us wake up to (via Mayo Clinic).
Next time you notice that your breath is a little off, try reaching for a glass of water rather than a mint. It’s worth noting, though chronic dry mouth can also be related to an issue with your salivary glands or some other condition, reported the Mayo Clinic, so be sure to consult your doctor if it’s a lingering issue.
You may be susceptible to diabetes
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When it comes to non-oral causes of bad breath, research points towards diabetes. People with diabetes are prone to dry mouth, tooth decay, and gum disease, which are well-known odor-causing oral health problems (via Mayo Clinic). A 2024 report in the IOSR Journal of Dental and Medical Sciences says that one in three diabetics will also encounter a periodontal disease.
Diabetes-related halitosis can also stem from elevated levels of ketones in the blood (via Live Science). This occurs in people with a condition called diabetic ketoacidosis. When the body does not make enough insulin to break down and use glucose as an energy source, it starts to metabolize fat instead. Ketones are produced in the process, which yield a sweet, fruity breath odor or a smell that’s reminiscent of acetone (via WebMD).
While it may not sound as troublesome as other kinds of odorous breath, ketoacidosis can become life-threatening in a short amount of time, so it’s important to consult your doctor if you think your breath might be signaling this condition.
You’re at risk for heart disease
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Medical and dental experts emphasize the close link between gum disease and heart problems, with gingivitis and periodontitis being considered as precipitators of cardiovascular disease (via Harvard Health Publishing). Various theories have been put forward to explain this connection, a key one being that the bacteria infecting the gums makes its way into the body’s blood vessels, causing inflammation and vascular damage throughout the body, which can bring on a blood clot, a stroke, and heart attack, per Harvard Health Publishing.
In support of this theory, a 2024 study showed that bacteria commonly detected in the mouth, namely a strain of streptococci, was also identified in the brains of people who suffered from a stroke. “Our results suggest that bacteria might have a role in the (development) of serious complications related to atherosclerosis,” Olli Patrakka, the study’s lead author, told the American Heart Association.
Another theory proposes that smoking is a risk factor — and the actual link — between gum disease and cardiovascular disease, as reported by Harvard Health Publishing. Irrespective of the underlying cause, it seems that a persistent case of bad breath could be a major indicator of cardiovascular risk and should not go ignored for too long.
You could have liver or kidney disease
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Lesser-known triggers of bad breath include liver and kidney damage. People with late-stage liver failure often have sweet, musty-smelling breath, also referred to as “fetor hepaticus”, which is brought on by volatile organic compounds (namely dimethyl sulfide) that accumulate in the body when the liver is malfunctioning (via Live Science). In light of this being a common symptom of liver pathologies, a breath analysis could help detect and diagnose liver disease, as proposed by the researchers of a 2008 study.
Additionally, people with chronic kidney failure tend to have breath that smells a bit fishy, or similar to ammonia or urine, explained Live Science. A 2024 study illustrates that when your kidneys are unable to filter and remove the waste products and chemicals from your blood, there’s a buildup of urea nitrogen in the blood, which also increases the concentration of urea in the saliva, thus causing an ammonia odor. The researchers cite breath ammonia detection as an inexpensive and useful screening method for kidney problems.
You may have Sjögren’s syndrome
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Your halitosis could be a warning sign of a serious health problem like Sjögren’s syndrome — a chronic autoimmune disease that is characterized by dry mouth and eyes, an abnormal sense of taste, and fatigue (via Cleveland Clinic). Since the illness affects the body’s glands that produce moisture, xerostomia (dry mouth) and reduced salivary flow are primary symptoms, reported a scientific article in Our Dermatology Online journal.
These conditions heighten the Gram-negative bacteria in the mouth that may result in infections, dental cavities, gum disease, tooth decay, and even tooth loss — all of which are major contributors to the volatile sulfur compounds that give rise to unpleasant odor of the mouth.
Sjögren’s syndrome is most common among women, noted the Cleveland Clinic. The underlying cause of the condition remains a mystery to most scientists and requires further research to be better understood. But some theories draw a possible connection between the illness and hormonal factors, while others have looked at the influence of viruses and genetics.
Certain medications are a contributing factor
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Certain prescription medications can bring on bad odor of the mouth, including antidepressants, antipsychotics, decongestants, antihistamines, and antihypertensive medications, according to research published in Journal of Natural Science, Biology and Medicine. These drugs cause a decrease in salivary flow, which comes with the unpleasant side effect of dry mouth — a favorable habitat for odor-causing bacteria to fester.
A 2024 literature review on drug-related halitosis identified nine potentially contributing medications. Researchers found that aside from the displeasing consequences of dry mouth, these drugs set off certain malodorous chemicals when processed and broken down by the body, which journey through the bloodstream and make their way to your breath. In particular, disulfiram is reduced to carbon disulfide — a stable compound in blood — while nitric oxide reacts with foul-smelling organosulfur compounds.
Some other medications raise the mouth’s pH level, encouraging the growth of gram-negative germs in the oral cavity, creating idyllic conditions for halitosis to thrive. The researchers concluded that halitosis can be triggered by a number of medications but does not necessarily correlate to any one particular disease or specific form of drug therapy.
