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Common Causes of Bad Breath & Treatment Options

Alyssa Hill Headshot
Written by
Alyssa Hill
Medically Reviewed by 
Dr. Lara Coseo
6 Sources Cited

What is Halitosis (Bad Breath)?

Halitosis, the medical term for bad breath, affects about 40 million Americans in the United States.

Bad breath is characterized by an unpleasant and persistent odor in exhaled breath that is typically not serious. There are a variety of causes of bad breath that are linked to poor dental hygiene, eating habits, or even dehydration.

The tongue also harbors bacteria, and if it is not brushed daily, halitosis can develop. In some cases, if halitosis persists even after brushing, it may be a sign of an underlying infection or disease.

Most people with chronic halitosis do not notice they have the condition. Although, licking the forearm and smelling it will typically indicate bad breath.

Halitosis also occurs less in vegetarians than meat-eaters. If the mouth is not cleaned properly, leftover meat particles will begin to decay and produce a foul smell.

Risk Factors & Causes of Halitosis

The cause of bad breath could be linked to lifestyle habits, diet, poor dental care, or an individual’s medical history. Common risk factors include:

Poor Oral Hygiene

Mouth fresheners, gums, and sprays could help temporarily if used in between flossing, brushing, and rinsing with chlorine dioxide mouthwash.

Chewing parsley, basil, mint, or cilantro also helps control bad breath.


Coffee is a highly acidic substance that can lead to dry mouth, tooth discoloration, and halitosis. However, rinsing with mouthwash, brushing, and flossing after drinking coffee reduces bad breath.


Alcoholic drinks and mouthwashes containing more than 25 percent alcohol can lead to halitosis.

Sugar and Processed Foods

Naturally occurring bacteria in the mouth feeds on sugars and results in a sour smell. So, you should eat a balanced diet to counteract the effects of unhealthy foods on your oral health and breath.

Smoking Tobacco

Cigarettes and other tobacco products, such as cigars and chewing tobacco, can cause bad breath and dry mouth. This is especially if your oral health is neglected as well.

Certain Medications

Blood pressure medications, such as beta-blockers, diuretics, alpha-blockers, and calcium channel blockers, can lead to halitosis. Antihistamines, tetracyclines, sulfa, antidepressants, and decongestants can also cause bad breath.

Dry Mouth

Dry mouth, also called xerostomia, is a non-life-threatening oral condition that occurs when the salivary glands in the mouth do not produce enough saliva to keep the mouth wet.

It is caused by insufficient fluid intake and certain prescription medications. Cancer treatments, such as chemo, can also result in thick saliva, causing dry mouth.

Xerostomia naturally occurs while you are sleeping and typically causes bad breath in the morning. In particular, adults who sleep with their mouths open are more likely to develop dry mouth.


Low-carb diets (ketosis), fasting, and high-protein diets can cause halitosis. This includes eating excessive amounts of eggs, dairy, and red meat. Not eating enough carbohydrates can also cause this condition.


Dehydration, mucus build-up, and tonsil infections can cause bad breath. Hormonal changes in women, especially during pregnancy, can result in bad breath as well.

Rare Causes of Bad Breath

The most common cause of bad breath is oral hygiene. However, other situations can also be to blame.

Rare causes of bad breath include:


When the insulin levels of someone with diabetes are very low, their bodies can no longer use sugar and use fat stores instead. When fat is broken down, ketones are made and build up. Ketones can be poisonous in large numbers and create a distinctive and unpleasant breath smell.

Bowel Obstruction

Breath can smell like feces if there has been an extended period of vomiting, especially if someone has a bowel obstruction.


This is a condition in which airways become wider than usual. This allows for a build-up of mucus, leading to bad breath.

Aspiration Pneumonia

This is a swelling or infection in the lungs or airways from inhaling vomit, saliva, food, or liquids, resulting in an unpleasant breath odor.


Breath smells can differ depending on the cause of the problem. It is best to ask someone close to check your mouth odor as it can be challenging to assess it yourself.

If nobody is available to help, one way to check the smell is to lick your wrist, leave it to dry, and then smell it. A bad odor on this area of the wrist may suggest that you have halitosis.

Some people worry about their breath even if they have little or no mouth odor. This condition is known as halitophobia, and it may lead to obsessive mouth-cleansing behavior.


A general dentist will often smell the breath of someone with suspected halitosis and rate it on a six-point intensity scale. The dentist may scrape the back of the tongue and check the scrapings for smell, as this area can typically be a source of the odor.

Several sophisticated detectors can rate the smell more accurately.

They include:

  • Halimeter: This picks up low levels of sulfur.
  • Gas chromatography: This test assesses three sulfur compounds, which are hydrogen sulfide, methyl mercaptan, and dimethyl sulfide.
  • BANA test: This measures levels of a certain enzyme created by halitosis-causing bacteria.
  • Beta-galactosidase test: This test checks levels of the enzyme beta-galactosidase, which is linked to bad mouth odor.

Treatment Options for Bad Breath

Halitosis typically goes away on its own with lifestyle changes and proper oral care. In particular, good oral care tips include:

Routine Dental Exams and Preventive Treatment

The American Dental Association (ADA) suggests that adults visit a dentist for regular exams and teeth cleanings at least twice a year (every six months).

During dental exams, a dentist or dental hygienist examines the mouth for cavities, decay, gum disease, and other oral health conditions.

Preventing Bad Breath

Brushing twice a day, flossing at least once a day, and rinsing the mouth with an alcohol-free mouthwash regularly kills bacteria and keeps the mouth healthy.

Brushing the tongue with a scraper also helps prevent bad breath.

Other halitosis prevention techniques and treatment options include:

  • Chewing Sugarless Gum (stimulates bacteria-fighting saliva).
  • Avoiding Toothpicks (they damage the gums and teeth).
  • Using anti-VSC Oral Care Products (they do not contain alcohol or zinc).
Last updated on April 5, 2022
6 Sources Cited
Last updated on April 5, 2022
All NewMouth content is medically reviewed and fact-checked by a licensed dentist or orthodontist to ensure the information is factual, current, and relevant.

We have strict sourcing guidelines and only cite from current scientific research, such as scholarly articles, dentistry textbooks, government agencies, and medical journals. This also includes information provided by the American Dental Association (ADA), the American Association of Orthodontics (AAO), and the American Academy of Pediatrics (AAP).
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  5. Naseem, Sajida et al. “Oral Hygiene Practices and Teeth Cleaning Techniques Among Medical Students.” Cureus vol. 9,7 e1487. 18 Jul. 2017
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