Bad Breath
Symptoms, Causes, Questions & Related Topics

Top 8 Bad Breath Causes

1. Smoking and Tobacco Use

Smoking can cause smoke particles to stay in the throat and lungs and emit a specific odor known as smoker’s breath. Chemicals in tobacco products can remain in the mouth and irritate gum tissue to cause bad breath. Tobacco users are more likely than non-users to suffer gum disease,[1] for which bad breath is also a symptom. Those who quit smoking and stop chewing tobacco products might be able to reverse problems with bad breath.

2. Dry Mouth

Also known as xerostomia, dry mouth is a condition in which the salivary glands in the mouth decrease saliva production and fail to generate enough saliva to keep the mouth wet. Saliva naturally helps rinse away bacteria in the mouth,[2] but lack of saliva can allow bacteria to build up and contribute to bad breath. Dry mouth can be caused by breathing through the mouth, snoring, and dehydration. Staying hydrated and eating regular meals throughout the day can prevent it.

3. Poor Oral Hygiene

Poor oral hygiene habits, such as not brushing or flossing regularly, can cause food particles to stay in the mouth and generate bacteria. Bacteria can coat the teeth, gums, and tongue to cause bad breath. Over time, bacteria can cause heavy plaque buildup that increases the risk for gum disease and persistent bad breath. Brushing at least twice per day and flossing at least once per day can help maintain good oral hygiene.[3]

4. Postnasal Drip

Postnasal drip is the accumulation of excess mucus in the nose or back of the throat. Mucus that stays in the throat and hardens in the tonsils can attract bacteria that contribute to bad breath. Dairy products, such as milk and cheese, can cause this mucus to thicken and worsen problems with bad breath. Chronic postnasal drip and related sinus problems can also cause bad breath.

Treating postnasal drip might help reverse problems with bad breath. Postnasal drip treatments include over-the-counter decongestants, antihistamines, and saline nasal sprays. Sleeping with the head slightly elevated and staying hydrated can also treat postnasal drip.[4]

5. Gastroesophageal Reflux Disease (GERD)

GERD is a digestive condition in which stomach contents flow back into the esophagus to irritate its lining.[5] The stomach acid and bile that passes back into the esophagus can cause unpleasant odors and bacteria buildup that leads to bad breath.

GERD treatments neutralize or reduce stomach acid or block acid production so the esophagus can heal. Lifestyle behaviors, such as quitting smoking and maintaining a healthy weight, can also treat GERD to reduce bad breath.[6]

6. Dental Infections

Cavities, surgical wounds, and gum disease are some dental conditions that can cause bad breath. Dental infections can attract bacteria and cause plaque buildup that contributes to bad breath. Seeing a dentist regularly while also practicing good nutrition and oral hygiene habits can help prevent dental infections.

7. Food

Garlic and onions contain sulfur compounds that linger in the mouth to cause bad breath and are also absorbed by the bloodstream to cause bad breath upon exhaling.[7] Coffee and alcohol can cause dehydration and dry mouth, which leads to bacteria buildup that causes bad breath. Protein-dense foods, acidic foods, and sugary foods are also linked to bad breath.[7] Smelly breath caused by eating these foods might be reduced by drinking more water and consuming fruits and vegetables high in nutrients that fight bad breath.[8]

8. Medications

Many over-the-counter and prescription medications list dry mouth and unpleasant breath odor as side effects. Medications linked to bad breath include antidepressants, birth control pills, hormone replacement therapy, and antihistamines.[9] Some medications facilitate certain bodily processes that can cause other conditions linked to bad breath. Bad breath caused by medications can be treated by replacing those medications with other therapies that effectively treat the health condition.

Possible Health Conditions Related to Bad Breath

  • Gum disease: A condition in which inflammation of gum tissue can lead to tooth loss, receding gums, and bad breath.
  • Oral thrush: A yeast infection that develops on the tongue and inside the mouth.
  • Dental cavities: Holes or cavities that develop in the teeth due to damaged enamel and cause symptoms that include tooth loss and toothache.
  • Pneumonia: An infection where one or both lungs become inflamed and fill with fluid to cause wet cough, difficulty breathing, fever, and chills.
  • Bronchitis: Inflammation of the airways to and from the lungs that causes shortness of breath and the coughing up of mucus.
  • Chronic sinusitis: A condition in which the cavities around sinuses become swollen and inflamed to cause headache, runny nose, and nasal congestion.
  • Diabetes: A condition where chronically high blood sugar inhibits insulin production or causes insulin resistance.
  • Chronic acid reflux: A condition where stomach acid and bile flows back up through the esophagus to cause heartburn and regurgitation.
  • Liver or kidney problems: Decreased liver and kidney function characterized by water retention, loss of appetite, swelling, and other symptoms.
  • Stomach cancer: Cancer in the stomach or lining of the stomach characterized by nausea, heartburn, bloating, and other symptoms.

Questions Your Doctor May Ask About Bad Breath

  • When did you first notice bad breath?
  • How often do you brush and floss your teeth?
  • Do you notice that certain foods cause your bad breath?
  • Is your bad breath occasional or constant?
  • Which medications and supplements do you currently use?
  • Do you suffer allergies or sinus problems?
  • Do you breathe through your mouth?
  • Do you snore?
  • What existing health problems do you have?
  • Do you smoke or use tobacco products?
  • How often do you eat and drink water?

Bad Breath May Also Be Known as

  • Halitosis
  • Smelly breath
  • Stinky breath
  • Foul breath
  • Dragon breath
  • Morning breath


  1. National Library of Medicine. Effect of cigarette smoking on the periodontal health status: A comparative, cross sectional study.
  2. National Library of Medicine. Oral Microbial Ecology and the Role of Salivary Immunoglobulin A.
  3. National Library of Medicine. Dental care — adult.
  4. Harvard Health Publishing. Treatments for post-nasal drip.
  5. National Institute of Diabetes and Digestive and Kidney Diseases. Acid Reflux (GER & GERD) in Adults.
  6. National Library of Medicine. Lifestyle changes as a treatment of gastroesophageal reflux disease: a survey of general practitioners in North Queensland, Australia.
  7. National Library of Medicine. Halitosis: From diagnosis to management.
  8. Glendale Community College. Nutrition or Bad Breath.
  9. University at Buffalo. The Mouthwash Debate.

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