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9 Conditions Your Breath Can Reveal

Checking your breath may not just save you from awkward social moments — it could also save your life. From lung cancer to kidney failure, find out what medical conditions doctors can detect by telling you to just open your mouth.
By
Alysha Reid
Updated on November 28, 2023
by
Justin Laube, MD

Next up video playing in 10 seconds

6 Conditions Your Breath Can Reveal

Discover health conditions that your breath might reveal.

Bad breath is embarrassing. But a quick breath check can save you from more than just an awkward social situation — it could save your life. Breath-test technology can detect stomach cancer in its earliest stages, according to one study.

However, stomach cancer isn’t the only medical condition your breath can reveal. According to the Mayo Clinic, bad-breath odors vary and depend on the underlying cause. Here are some common bad-breath causes:

  • Food As food particles break down in the mouth, bacteria increase, resulting in bad odors. Onions, garlic, and certain spices are common bad-breath causes.
  • Tobacco Products Smoking tobacco also results in smelly breath, as does chewing tobacco.
  • Poor Dental Habits Not flossing or brushing your teeth regularly is a common cause of bad breath. This happens when tiny bits of food stay trapped in your mouth. Your tongue can be another bad-breath cause as bacteria coats it, causing foul odors.
  • Dry Mouth A condition called dry mouth can cause bad breath as saliva in the mouth is reduced. Dry mouth is a common cause of morning breath, especially in people who sleep with their mouth open.
  • Dental Infections Tooth decay, gum disease, surgical wounds, and dying teeth are all causes of bad breath.
  • Postnasal Drip Mucus that hardens in the tonsils can be a cause of bad breath. Chronic postnasal drip and sinus drainage are also bad-breath causes.
  • GERD An acidic stomach or chronic reflux of stomach acid (gastroesophageal reflux disease, or GERD) is linked to bad breath. Treating GERD may cure the bad breath.
  • Other Serious Causes Some types of cancer and metabolic diseases can leave a distinctive breath smell. Talk to your doctor if you detect a metallic or other odor.

Some people worry too much about their breath even though they have little or no mouth odor, while others have bad breath and don’t know it. Because it’s difficult to assess how your own breath smells, ask a close friend or relative to confirm your bad-breath worries.

Poor dental hygiene accounts for most cases of bad breath, also known as halitosis. However, bad breath can sometimes signal another underlying medical condition. And you don’t have to give off an odor, either: Even the freshest breath can be screened for various health problems.

1

Breath Tests May Diagnose Lung Cancer

a doctor looking at an xray to check for lung cancer
Thinkstock

Could lung cancer be a cause of bad breath? Pathologists normally perform biopsies and ultrasound scans to diagnose lung cancer, but using breath tests may be a cheaper, noninvasive alternative, according to one study. Researchers used a preprogrammed “electronic nose,” which detects different profiles of volatile organic compounds (VOCs) in exhaled breath, to examine breath samples from 475 subjects. The group included a mix of 252 lung cancer patients, 223 patients with different lung conditions and healthy volunteers, 265 smokers, and 210 nonsmokers.

They found that among the nonsmokers, the electronic nose accurately identified lung cancer in 128 subjects and misdiagnosed in only 5. Among smokers, the electronic nose correctly identified 114 people as having lung cancer, misdiagnosing 5.

What’s more, a study found that accuracy of breath tests to detect lung cancer continues to improve, thanks to the use of more specific VOCs.

2

Heart Failure May Be Diagnosed With Breath Samples

a heart beat, which can represent heart failure
Thinkstock

Researchers at the Cleveland Clinic used a simple breath test to identify patients suffering from heart failure, according to a paper.

The researchers collected breath samples from 41 patients admitted into a hospital — 25 with severe heart failure and 16 with other heart-related problems. Researchers then used mass spectrometric technology to analyze the breath samples for molecular and chemical compound signs of heart failure. They were able to detect two volatile compounds, acetone and pentane, that were elevated in heart failure patients and were able to distinguish these patients from controls.

Research continues to evolve in this area. A newer study found that heart failure patients with higher levels of acetone of pentane were more likely to have adverse outcomes and death, compared to heart failure patients with lower levels, 33 months later.

3

Fruity or Acetone Breath May Indicate Diabetes Complications

`a woman with diabetes checking her blood sugar
Alamy

Poorly managed diabetes can make you more susceptible to gum disease and dry mouth. When your blood sugar levels aren’t stable, your weakened body isn’t able to fight bacteria that can cause infections that harm the gums. These same infections cause bad breath.

A fruity breath odor or an odor similar to acetone (commonly used in nail polish remover) can also point to a serious complication in patients with diabetes called ketoacidosis, according to a study. When your body doesn’t have enough insulin, it instead uses fatty acids for energy, which produces acidic ketones. These acids can accumulate in your blood and lead to a diabetic coma or death.

4

Fishy Breath May Be a Sign of Kidney Failure

illustration of kidneys, which can represent kidney failure
Thinkstock

Fishy breath isn’t always from seafood: A mouth that smells like fishy-odor urine, similar to ammonia, may indicate kidney failure.

The kidneys remove toxic chemicals from the blood by creating urine. In kidney failure, also known as end-stage renal disease, the kidneys become so damaged that they are no longer able to filter waste products and toxic chemicals from the blood. When this happens, the dangerous toxins and waste not discharged from your body accumulate and affect nearly every part of your body.

The fishy-breath odor can occur when kidney failure affects the respiratory system and causes breathing problems, according to a study.

5

Sleep Apnea Can Cause Morning Breath

a man with sleep apnea as he sleeps in bed
Thinkstock

Morning breath may seem normal after a night of sleeping. Saliva production decreases during sleep, which gives odor-producing bacteria an opportunity to multiply and grow.

But the slowed production of saliva during sleep can sometimes be caused by leaving your mouth open for long periods of time. People with sleep disorders such as sleep apnea and snoring may have trouble breathing through the nose and are more likely to breathe through their mouths, which is a cause of bad breath, according to the Cleveland Clinic.

6

GERD May Be a Cause of Bad Breath

a man with gerd which can cause bad breath
Thinkstock

Digestive conditions such as acid reflux and gastroesophageal reflux disease (GERD) are bad-breath causes. Both digestive conditions can delay or prevent food from processing efficiently in the stomach. When food doesn’t move through the digestive system, it can start to decay. Small amounts of undigested food may even regurgitate and cause bad breath. Dentists may also detect GERD in patients when they notice an inflamed red throat and acid erosion in the teeth.

But GERD isn’t the only digestive health issue that can affect your breath. One study suggests that the H. pylori bacteria that cause stomach ulcers can be a cause of bad breath.

7

Allergies and Postnasal Drip May Lead to Foul Breath

a woman blowing her nose because of allergies
iStock.com

Respiratory tract infections such as the flu, bronchitis, and sinusitis are common causes of bad breath. When respiratory tract infections break down or inflame the tissues in the respiratory system, it can trigger the production of bacteria-feeding cells and mucus.

Allergies and postnasal drip may also be what causes bad breath because these conditions tend to clog your nose. This nasal congestion may force you to breathe through your mouth, which can lead to dryness and the growth of bacteria that cause foul breath.

8

Stop Bad Breath Linked to Tooth Decay and Gingivitis

a dentist showing the proper way to brush teeth
Thinkstock

When the enamel on your teeth erodes, food particles can get deposited in those holes, called dental caries. Because brushing your teeth can’t remove these food deposits, they can eventually grow bacteria, which is what causes bad breath.

Gingivitis is another medical condition that causes bad breath. When your gums become inflamed with bacteria, it can result in severe pain and funky-smelling discharge.

9

Stomach Cancer Is a Serious Cause of Bad Breath

illustration of a person's stomach
Thinkstock

Routine screening for stomach cancer in the United States is uncommon, largely because the current method — endoscopy — is invasive. But that may change with the development of breath-test technology called nanoarray analysis, which identifies the levels of certain compounds that are linked to stomach cancer.

In a study of 335 patients — 163 who had been diagnosed with oesophageal or gastric cancer — the breath test identified cancer from benign diseases with 85 percent accuracy.

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Additional Sources
  • Amal H et al. Detection of Precancerous Gastric Lesions and Gastric Cancer Through Exhaled Breath. Gut. March 2016.
  • Bad Breath: Symptoms and Causes. Mayo Clinic. March 10, 2018.
  • Tirzïte M et al. Detection of Lung Cancer With Electronic Nose and Logistic Regression Analysis. Journal of Breath Research. November 20, 2018.
  • Fu XA et al. Noninvasive Detection of Lung Cancer Using Exhaled Breath. Cancer Medicine. February 2014.
  • Samara MA et al. Single Exhaled Breath Metabolomic Analysis Identifies Unique Breathprint in Patients With Acute Decompensated Heart Failure. Journal of the American College of Cardiology. April 2, 2013.
  • Tang WHW et al. Exhaled Breath Analysis Using Selected Ion Flow Tube Mass Spectrometry and Disease Severity in Heart Failure. Metabolites. October 3, 2023.
  • Sapra A et al. Diabetes. StatPearls. June 21, 2023.
  • Sorino C et al. When Kidneys and Lungs Suffer Together. Journal of Nephrology. October 2019.
  • Mouth Breathing. Cleveland Clinic. April 11, 2022.
  • Suzuki N et al. Detection of Helicobacter Pylori DNA in the Saliva of Patients Complaining of Halitosis. Journal of Medical Microbiology. December 2008.
  • Markar SR et al. Assessment of a Noninvasive Exhaled Breath Test for the Diagnosis of Oesophagogastric Cancer. JAMA Oncology. July 1, 2018.

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