Good news for bad breath

Unmasked and unexpected

During the recent “COVID years,” we all experienced the many complications associated with wearing a mask. Besides being uncomfortable, hot, and annoying, it may have been the first time we had to smell and endure rebreathing our own breath.

Person wears a mask

Be aware that people with bad breath can’t smell their own breath (unless they are wearing a mask). (Stock image.)

SURPRISE! For those thinking, “Lucky me, I’m sure glad I don’t have bad breath,” be aware that people with bad breath can’t smell their own breath (unless they also are wearing a mask). Most people become accustomed to their own breath, so they don’t know if it smells OK or horrible. Also, when we sniff, trying to smell our breath, we’re breathing air from below rather than in front (where we exhale). Either way, the mouth air in chronic malodor sufferers is tainted with compounds that produce a foul and often offensive air stream.

Bad breath usually originates in the mouth and describes with different names such as oral malodor, foetor ex ore (Latin, meaning stench mouth), and halitosis (derived from the Latin word halitus, meaning ‘breath,’ and the Greek suffix -osis meaning ‘diseased’ or ‘a condition of.’ The origins of the term halitosis date to physician Joseph William Howe’s 1874 book The Breath, and the Diseases which Give it a Fetid Odor.

Halitosis’s malodor includes compounds that smell like feces (caused by scatole–3-methylindole), the rotten egg smell of hydrogen sulfide gas, or a corpse-like aroma from cadaverine (toxic ptomaine, C5H14N2). The odor may smell of rotten fish, sweaty feet, decaying meat, or even human urine. Yikes.

The major compounds that contribute to oral malodor are volatile sulfur compounds (VSCs), mainly hydrogen sulfide. Bacteria in the mouth, predominantly on the back of the tongue, can produce these odorous sulfur compounds through the process of decay or the rotting of organic sulfur-containing proteins, termed putrefaction.

A little history

Yellow teeth

Early Islamic theology stressed that the teeth and tongue should be cleaned with a siwak (a small stick). (Stock image.)

The earliest mention of bad breath was in ancient Egypt, where detailed recipes for toothpaste were found well before the Pyramids rose. A papyrus dating to 1550 BCE describes attempts to cure bad breath using incense, cinnamon, myrrh, and honey. Later, Hippocrates advocated a mouthwash cure comprising red wine and spices.

Ancient Chinese emperors required visitors to chew cloves before an audience. The Talmud describes bad breath as a disability that was grounds for divorce. Early Islamic theology stressed that the teeth and tongue should be cleaned with a siwak (a small stick).


Epidemiological studies report halitosis prevalence between 2.4% and 78% of the world’s population, while the American Dental Association reports nearly 50% of American adults suffer from oral malodor, including different forms of halitosis. The reason for such high variability in prevalence is the result of different methods used for assessment — whether data is based on self-reporting or objective measurements; the geographic location; and the year when the study was performed. At least 50% of the population has persistent effects of oral malodor, and half of these people suffer from chronic halitosis. Oral malodor is considered the third-highest cause of dental office visits, behind dental caries and periodontal diseases. Moreover, Americans spend about $1 billion annually on oral rinses, mints, and over-the-counter products. That’s a lot of money!

Halitosis causes and diagnoses

Ooh, your breath smells bad

Without knowing the precise cause, people typically attempt to mitigate oral malodor by trying to reduce their mouths’ bacterial load with antiseptic mouth rinses, mints and candies, sprays, and flavored gums. (Stock image.)

Diagnosing halitosis usually begins with the individual or a close confidant. Determining the cause of genuine halitosis requires a rigorous medical history, physical examination, and knowledge of the possible etiology.

Halitosis includes three major categories:

  • genuine halitosis
  • pseudo-halitosis
  • halitophobia (severe fear of bad breath that doesn’t exist)

Genuine halitosis subclassifies into physiologic halitosis and pathologic halitosis. Physiologic halitosis arises through putrefactive processes (decay and rotting usually caused by bacteria) within the oral cavity without any related pathologic condition. The implicated bacteria are located in the oral cavity’s stagnant areas, primarily the tongue’s rear region (dorsal surface), and in dental plaque. These bacteria release VSCs that identify as bad breath, regardless of their origin.

Extraoral sources of halitosis are responsible for 10%-20% of all cases and are caused by poor diet, alcohol abuse, tobacco smoking, certain drugs, and diseases of the digestive tract as well as some systemic conditions.

Pseudo-halitosis is the condition in which a person stubbornly complains of oral malodor, which is not perceived by others.


Tongue scraper

Tongue cleaning seems to work more through reducing the substrates for putrefaction, rather than the bacteria themselves. (Stock image.)

OK, so what can we do if we discover we have halitosis? It depends on whether the cause is inter- or extraoral. Without knowing the precise cause of the “oral malodor,” people try to mitigate the problem by attempting to reduce their mouth’s bacterial load with antiseptic mouth rinses, mints, sprays, and flavored gums. Some people even get their tonsils removed, believing this will stop the malodor. Most of the time it does not!

Several treatment options exist for intraoral malodor. Mechanically, you can disrupt the tongue’s bacteria with various back-of-the-tongue-scraping techniques — though tongue cleaning seems to work more through reducing the substrates for putrefaction rather than the bacteria. Unfortunately, mouth rinses and pastes — including amine stannous fluoride, baking soda, hydrogen peroxide, ethyl alcohol, zinc chloride, eucalyptus oil, essential oils and extracts, and oils of peppermint, spearmint, and wintergreen — are minimally effective for short periods.

Foods that cause and help halitosis

For many individuals, the substrates for VSC production are sulfur-containing amino acids derived mainly from foods, primarily animal protein, as well as many plant-based foods like different nuts, seeds, grains, and legumes, as well as some leafy green vegetables, leeks, curry, and garlic.


Research suggests that limiting animal proteins, fats and alcohol consumption may significantly reduce mouth malodor. (Stock image.)

Research suggests that limiting the consumption of animal proteins, fats, and alcohol may significantly reduce mouth malodor. This is because fats and alcohol can cause relaxation of the lower esophageal sphincter. Typically, burping is the only time a person exhales odors from the stomach. This is because the sphincter located at the top of the stomach prevents gases from moving up and through the mouth. A diet rich in alcohol and fat relaxes that sphincter, increasing the risk and severity of bad breath.

Most cases of halitosis occur due to food-decaying residues in the mouth by the bacteria that decompose proteins and amino acids and produce VSCs as a by-product. Thus, researchers hypothesize that perhaps the treatment of halitosis should also include dietary changes.

Dairy proteins, for example, are known to break down in the mouth, leading to the release of amino acids rich in VSCs. Dairy products contain casein, rich in the sulfur-containing amino acid cysteine. When cysteine degrades, it produces hydrogen sulfide (a colorless gas with a strong rotten-egg odor), a key contributor to the bad-breath bouquet, and sulfhydryl anions (a negatively charged ion) that favors growth of the very bacteria within the mouth responsible for the protein putrefaction that produces oral malodor in the first place.

Hydrogen sulfide reacts with collagen, which can alter protein structures that promote periodontal pockets of putrid pus that can lead to more halitosis. These pockets are the second primary source of VSCs.

What to do about extra-oral halitosis?

Many culprits responsible for halitosis, including several drugs and dietary supplements (fish oil), don’t originate in the mouth. This is termed extra-oral halitosis. And then, there are other substances that cause people to smell fishy, primarily trimethylamine (TMAU).

Codfish or something quite disgusting

There are many culprits, including several drugs and dietary supplements (fish oil) responsible for halitosis that don’t originate in the mouth. (Stock image.)

Trimethylaminuria appears to be the primary cause of undiagnosed body fish odor. Trimethylamine forms in the gut and liver after consuming foods or supplements containing choline. Choline presents as an essential nutrient and is neither a vitamin nor a mineral, but it shares some similarities to B vitamins. The brain and nervous system tissues require choline to regulate memory, mood, and muscle functioning. Choline also serves as a precursor for some neurotransmitters and is involved in other essential bodily functions.

The richest dietary sources of choline include beef liver, chicken liver, eggs, tilapia, cod, salmon, cauliflower, broccoli, some legumes, and soybean oil. Two eggs can supply about 50% of the daily choline requirement.

At high concentrations, trimethylamine has an ammonia-like odor that can cause necrosis (death) of mucous membranes. At low concentrations, it has a rotting, “fishy” smell. The fish odor presentation may only occur in about 10% of individuals with this predisposition. Because many individuals consume foods rich in choline, most people — including doctors — may not make the connection between diet and body odor.

As always, you are what you eat!

  • Akaji, E.A., “Halitosis: A review of the literature on its prevalence, impact, and control.” Oral Health and Preventive Dentistry. 2014;12(4):297.
  • Feller, L., Blignaut, E., “Halitosis: A review. South African Dental Journal. 2005;60(1):17.
  • Forum, S.J., et al., “A narrative review of the diagnosis, etiology, and treatment of halitosis over the past three decades.” The Compendium of Continuing Education, Dentistry. 2022 May;43(5):E5-eE8.
  • Howe, J.W., “The breath and the diseases which give it a fetid odor.” New York, NY: Appleton & Co; 1874.
  • Izidoro, C. et al., “Revisiting standard and novel therapeutic approaches in halitosis: A Review.” International Journal of Environmental Research and Public Health. 2022 Sep 8;19(18):11303.
  • Kleinberg, I., Codipilly, D.M., “Cysteine challenge testing: A powerful tool for examining oral malodour processes and treatments in vivo.” International Dental Journal. 2002;52 Suppl 3:221.
  • Kloster, I., Erichsen, M.M., “Trimethylaminuria. Tidsskr Nor Laegeforen.” 2021 Sept. 10;141. English, Norwegian. doi: 10.4045/tidsskr.21.0142. PMID: 34597008.
  • Krespi, Y.P., et al., “Laser tongue debridement for oral malodor — A novel approach to halitosis.” American Journal of Otolaryngology. 2021;42(1):102458.
  • LaMotte, S., “Bad breath behind the coronavirus mask? 10 reasons and remedies for your halitosis.” CNN. May 5, 2020.
  • Llanos do Vale, K., et al. “Treatment of halitosis with photodynamic therapy in older adults with complete dentures: a randomized, controlled, clinical trial.” Photodiagnosis and Photodynamic Therapy. 2021;33:102128.
  • Mortazavi, H., et al., “Drug-related halitosis: A systematic review.” Oral Health and Preventive Dentistry. 2020;18(1):399.
  • Nagraj, S.K., et al., “Interventions for managing halitosis.” Cochrane Database Syst Rev. 2019;12(12): CD012213.
  • Pedrazzi, V., et al., “Tongue-cleaning methods: a comparative clinical trial employing a toothbrush and a tongue scraper.” Journal of Periodontology. 2004;75(7):1009.
  • Shon, H.S., et al., “Intra-oral factors influencing halitosis in young women.” Osong Public Health and Research Perspectives. 2018;9(6):340.
  • Silva, M.F., et al., “Estimated prevalence of halitosis: A systematic review and meta-regression analysis.” Clinical Oral Investigations. 2018;22(1):47.
  • Singh, V.P., et al., “Assessment and management of halitosis.” Dental Update. 2015;42(4):346-8, 351.
  • Vandekerckhove, B., et al., “Epidemiology in the general population, specific populations, and in a multidisciplinary halitosis consultation.” In: Ademgeur
  • Houten; Prelum Uitgevers: Houten, The Netherlands, 2009; pp. 3–10.

Leave a comment: