Bad Breath: Causes, Symptoms, Diagnosis, Classification, Epidemiology, Etymology and Treatment

Also known as halitosis , it is a symptom in which a noticeably unpleasant odor is present in the breath.

It can cause anxiety among those affected. It is also associated with depression and the symptoms of obsessive-compulsive disorder .

Worries about bad breath can be divided into genuine and not genuine cases. Of those who have genuine bad breath, about 85% of cases come from inside the mouth.

It is believed that the remaining cases are due to disorders of the nose, sinuses, throat, lungs, esophagus or stomach. Rarely, bad breath may be due to an underlying medical condition, such as liver failure or ketoacidosis.

Non-genuine cases occur when someone feels they have bad breath but someone else can not detect it. It is estimated that it represents between 5% and 72% of cases.

The treatment depends on the underlying cause. Initial efforts may include tongue cleaning, mouthwash and flossing. Provisional tests support the use of mouth rinses containing chlorhexidine or cetylpyridinium chloride.

While there is a tentative benefit of using a tongue cleaner, it is not enough to draw clear conclusions. Treating underlying conditions such as gum disease, tooth decay or gastroesophageal reflux disease may help.

Counseling may be useful in those who falsely believe they have bad breath. The estimated rates of bad breath vary from 6% to 50% of the population.

Worry about bad breath is the third most common reason why people seek dental care, after tooth decay and gum disease. It is believed to become more common as people get older.

Bad breath is seen as a social taboo and those affected can be stigmatized. People in the United States spend more than $ 1 billion per year on mouthwash to treat the condition.



In about 90% of the genuine cases of halitosis, the origin of the smell is in the mouth itself. This is known as intraoral halitosis, oral malodor or oral halitosis.

The most common causes are the biofilm that produces odor on the back of the tongue, below the gum line and in the pockets created by gum disease between the teeth and gums.

This biofilm results in the production of high levels of bad odors.

Odors occur mainly due to the breakdown of proteins into individual amino acids, followed by the further degradation of certain amino acids to produce detectable toxic gases.

Volatile sulfur compounds are associated with oral malodor levels, and generally decrease after successful treatment.

Other parts of the mouth may also contribute to the general smell, but they are not as common as the back of the tongue.

These places are, in order of descending prevalence, interdental and subgingival niches, defective dental work, areas of food retention between the teeth, abscesses and dirty dentures.

Oral lesions caused by viral infections such as herpes simplex and HPV can also contribute to bad breath.

The intensity of bad breath can vary during the day, due to certain foods (such as garlic, onion, meat, fish and cheese), smoking, and alcohol consumption.

Since the mouth is exposed to less oxygen and is inactive during the night, the odor usually worsens upon waking up “morning breath”.

Bad breath can be transient, often disappearing after eating, drinking, brushing teeth, flossing or rinsing with specialized mouthwash.

Bad breath can also be persistent (chronic bad breath), which affects approximately 25% of the population to varying degrees.


The most common location for halitosis related to the mouth is the tongue. Bacteria of the tongue produce malodorous compounds and fatty acids, and represent 80% to 90% of all cases of bad breath related to the mouth.

Large quantities of natural bacteria are often found on the back of the tongue, where normal activity keeps them relatively immutable.

This part of the tongue is relatively dry and poorly cleaned, and the intricate microbial structure of the back of the tongue provides an ideal habitat for anaerobic bacteria, which flourish under a continuous lingual coating of food debris, dead epithelial cells, nasal drip and overlaying bacteria, living and dead.

When left on the tongue, anaerobic respiration of such bacteria can produce the putrescent odor of indole, skatole, polyamines or the “rotten egg” odor of volatile sulfur compounds (VSC) as hydrogen sulfide, methyl mercaptan, methyl and allyl sulfide and dimethyl sulfide.

The presence of halitosis producing bacteria on the back of the tongue should not be confused with the lingual coating. Bacteria are invisible to the naked eye, and degrees of white tongue coating are present in most people with and without halitosis.

A visible layer of white tongue does not always equal the back of the tongue as the origin of halitosis, however, it is thought that a “white tongue” is a sign of halitosis.

In oral medicine in general, a white tongue is considered a sign of several medical conditions.

It was shown that patients with periodontal disease have a six-fold higher prevalence of tongue coating compared to normal subjects.

Patients with halitosis also showed significantly higher bacterial loads in this region compared to individuals without halitosis.


Gingival cracks are small grooves between the teeth and gums, and they are present in health, although they can swell when there is gingivitis.

The difference between a gingival crevice and a periodontal pocket is that the anterior is <3mm deep and the last is> 3mm.

Periodontal pockets usually accompany periodontal disease (gum disease). There is some controversy about the role of periodontal diseases in the cause of bad breath.

However, advanced periodontal disease is a common cause of severe halitosis. The waste products of anaerobic bacteria that grow below the gum line (subgingival) have a nauseating smell and have been clinically shown to produce very intense bad breath.

It has been shown that the elimination of the subgingival calculus (ie, tartar or hard plaque) and friable tissue improves the odor of the mouth considerably. This is achieved by subgingival scaling and root planing and irrigation with a mouth rinse with antibiotics.

The bacteria that cause gingivitis and periodontal disease (periodontopathogens) are invariably gram negative and capable of producing volatile sulfur compounds.

It is known that methyl mercaptan is the major contributor of volatile sulfur compounds in halitosis caused by periodontal disease and gingivitis.

It has been shown that the level of volatile sulfur compounds in respiration correlates positively with the depth of the periodontal pocket, the number of bags and whether the bags bleed when examined with a dental probe.

In fact, volatile sulfur compounds have been shown to contribute to the inflammation and tissue damage characteristic of periodontal disease.

However, not all patients with periodontal disease have halitosis, and not all patients with halitosis have periodontal disease.

Although patients with periodontal disease are more likely to suffer from halitosis than the general population, the halitosis symptom showed a stronger association with the degree of coating of the tongue than with the severity of periodontal disease.

Another possible symptom of periodontal disease is a bad taste, which does not necessarily accompany a bad smell that others can detect.

Other causes

Other less common reported causes inside the mouth include:

Deep carious lesions (dental caries) that cause localized impaction and food stagnation.

Recent extraction dental plugs : filled with blood clots and provide an ideal habitat for bacterial proliferation.

Interdental food packaging (foods are pushed down between the teeth): this may be due to missing teeth, slanted, spaced or crowded teeth, or poorly contoured proximal dental fillings.

The remains of food are trapped, they experience slow bacterial putrefaction and release of malodorous volatile substances.

The food packaging can also cause a localized periodontal reaction, characterized by dental pain that is relieved by cleaning the food packaging area with interdental brush or dental floss.

Acrylic dentures (plastic false teeth) : inadequate hygiene practices of dentures, such as lack of cleaning and removal of the prosthesis every night, can cause a bad smell of the plastic or mouth as the microbiota responds to the Altered environment.

The plastic is really porous, and the mounting surface is usually irregular, sculpted to fit the oral edentulous anatomy. These factors predispose to bacterial and yeast retention, which is accompanied by a typical odor.

Oral infections, oral ulceration, stress and / or anxiety, alcohol.

Menstrual cycle : in the middle of the cycle and during menstruation, volatile sulfur compounds increased in women.

Smoking : Smoking is related to periodontal disease, which is the second most common cause of oral malodor. Smoking also has many other negative effects on the mouth, from increased rates of tooth decay to premalignant lesions and even oral cancer.

Volatile foods : onion, garlic, durian, cabbage, cauliflower and radish. They can leave malodorous residues that are subject to bacterial putrefaction and the release of sulfur compounds. However, they can also cause halitosis through the mechanism of halitosis carried by the blood.

Medications : often, medications can cause xerostomia (dry mouth), which increases microbial growth in the mouth.

Nose and sinuses

In this case, the air that comes out of the nostrils has an acrid odor that differs from the oral odor. Nasal odor may be due to sinus infections or foreign bodies.

Halitosis is often considered a symptom of chronic rhinosinusitis , however, gold standard breath analysis techniques have not been applied. Theoretically, there are several possible mechanisms of objective and subjective halitosis that may be involved.


There is disagreement as to the proportion of halitosis cases that are caused by the conditions of the tonsils. Some claim that the tonsils are the most important cause of halitosis after the mouth.

According to one report, approximately 3% of halitosis cases were related to the tonsils.

The conditions of the tonsils that can be associated with halitosis include chronic caseous tonsillitis (cheeselike material can be exuded from the tonsillar crypt), tonsillitis (tonsillitis) and, less frequently, peritonsillar abscess, actinomycosis, fungal neoplasms, chondroid coryroid and myofibroblastic tumor inflammation


The lower esophageal sphincter, which is the valve between the stomach and the esophagus, may not close properly due to a hiatal hernia or gastroesophageal reflux disease (GERD), which allows the acid to enter the esophagus and escape of gas into the mouth .

Zenker’s diverticulum can also cause halitosis due to aging of the food retained in the esophagus.


The stomach is considered by most researchers as a very rare source of bad breath.

The esophagus is a closed and collapsed tube, and the continuous flow of gas or putrid substances from the stomach indicates a health problem, such as a reflux severe enough to raise the contents of the stomach or a fistula between the stomach and the esophagus, which will show more serious manifestations than just a bad smell.

In the case of allylic methyl sulfite (the by-product of garlic digestion), the odor does not come from the stomach, since it is not metabolized there.

Systemic diseases

There are some systemic (non-oral) medical conditions that can cause bad breath, but these are rare in the general population. Such conditions are:

  • Fetor hepaticus ( hepatic stench ) an example of a rare type of bad breath caused by chronic liver failure.
  • Infections of the lower respiratory tract (bronchial and pulmonary infections).
  • Kidney infections and renal failure.
  • Carcinoma.
  • Trimethylaminuria “fish odor syndrome”.
  • Diabetes mellitus.
  • Metabolic conditions, resulting in a high blood dimethyl sulfide.
  • People affected by the above conditions often show additional symptoms more conclusive diagnoses than bad breath alone.

Halitosis delirante

A quarter of people seeking professional advice about bad breath have an exaggerated worry about having bad breath, known as halitophobia, delusional halitosis or as a manifestation of the olfactory reference syndrome.

They are sure that they have bad breath, although many have not asked anyone for an objective opinion. Bad breath can severely affect the lives of around 0.5-1.0% of the adult population.


Self diagnosis

Scientists have long believed that sniffing one’s breath is often difficult due to acclimation, although many people with bad breath can detect it in others.

Research has suggested that self-assessment of halitosis is not easy due to preconceived notions of how bad we think it should be.

Some people assume that they have bad breath due to bad taste (metallic, sour, fecal, etc.), however, bad taste is considered a bad indicator.

Patients often self-diagnose by asking a close friend.

A popular home method to determine the presence of bad breath is to lick the back of the wrist, let the saliva dry for one or two minutes and smell the result.

This test results in an overestimation, as concluded from the investigation, and should be avoided.

A better way would be to lightly scrape the backside of the tongue with a disposable plastic spoon and smell the drying residue.

Home tests that use a chemical reaction to evaluate the presence of polyamines and sulfur compounds in lingual swabs are already available, but there are few studies that show how well they detect the smell.

In addition, since the smell of the breath changes intensity throughout the day depending on many factors, multiple test sessions may be necessary.


If bad breath is persistent and all other medical and dental factors have been ruled out, specialized tests and treatments are required.

Hundreds of dental offices and commercial respiratory clinics now claim that they must diagnose and treat bad breath. They often use some of the various laboratory methods to diagnose bad breath:

Halimeter : a portable sulfide monitor used to assess the levels of sulfur emissions (to be specific, hydrogen sulfide) in the air in the mouth.

When used correctly, this device can be very effective in determining the levels of certain volatile bacteria that produce sulfur compounds. However, it has drawbacks in clinical applications.

For example, other common sulfides (such as mercaptan) are not recorded as easily and can be misrepresented in test results. Certain foods such as garlic and onions produce sulfur in the breath for up to 48 hours and can lead to false readings.

The Halimeter is also very sensitive to alcohol, so you should avoid drinking alcohol or using rinses that contain alcohol for at least 12 hours before the test.

This analog machine loses sensitivity over time and requires periodic recalibration to maintain accuracy.

Gas chromatography : portable machines are currently being introduced, such as the OralChroma .

This technology is specifically designed to digitally measure the molecular levels of the three main volatile sulfur compounds in a buccal air sample (hydrogen sulfide, methyl mercaptan and dimethyl sulfide).

It is necessary to measure the sulfur components of respiration and produces visual results in graphic form through the computer interface.

BANA test : this test is aimed at finding the salivary levels of an enzyme that indicates the presence of certain bacteria related to halitosis.

Β-galactosidase test : salivary levels of this enzyme correlated with oral malodor.

Although such instrumentation and examinations are widely used in respiratory clinics, the most important measure of bad breath (the gold standard) is sniffing and level score and the type of odor carried out by trained experts “organoleptic measures” .

The odor level is usually evaluated on a six-point intensity scale.


There are two main classification schemes for bad breath, although none of them is universally accepted.

The Miyazaki et al . the classification was originally described in 1999 in a Japanese scientific publication, and since then it has been adapted to reflect American society, especially with respect to halitophobia.

The classification assumes three primary divisions of the halitosis symptom, namely, genuine halitosis, pseudohalitosis, and halitophobia.

It has been suggested that this classification is the most used, but has been criticized because it is too simplistic and, to a large extent, is only useful for dentists instead of other specialties. The classification of Tangerman and Winkel was suggested in Europe in 2002.

This classification focuses only on those cases in which there is genuine halitosis, and has therefore been criticized for being less clinically useful for dentistry compared to Miyazaki et al . classification.

Any symptom of halitosis is potentially the sum of these types in any combination, superimposed on the physiological odor present in all healthy individuals.

How to avoid and fight bad breath

Efforts may include physical or chemical means to decrease the number of bacteria, odor masking products or chemicals to alter the odor generating molecules.

It is recommended that those who use tobacco products stop. The evidence does not support the benefit of changes in diet or chewing gum.

Mechanical measurements

Brushing your teeth can help. While there is a tentative benefit of cleaning the tongue, it is not enough to draw clear conclusions. A 2006 Cochrane review found provisional evidence that it could lower levels of odor molecules.

Flossing can be useful.

Mouth rinses

A 2008 systematic review found that antibacterial mouth rinses can help.

Mouthwashes often contain antibacterial agents that include cetylpyridinium chloride, chlorhexidine, zinc gluconate, essential oils, hydrogen peroxide, and chlorine dioxide.

Cetylpyridinium chloride and chlorhexidine can temporarily stain the teeth.

Underlying disease

If gum disease and cavities are present, it is recommended to treat them.

If it is believed that diseases outside the mouth contribute to the problem, treatment may lead to improvements. Counseling may be useful in those who falsely believe they have bad breath.


It is difficult for researchers to make estimates of the prevalence of halitosis in the general population for several reasons.

First, halitosis is subject to taboo and social stigma, which may affect the willingness of people to participate in such studies or to accurately report their experience about the condition.

Second, there is no universal agreement on what diagnostic criteria and what screening methods should be used to define which individuals have halitosis and which do not.

Some studies are based on self-reported halitosis estimation, and there is controversy about whether this is a reliable predictor of real halitosis or not. Reflecting these problems, the epidemiological data reported are widely variable.

History, society and culture

The earliest known mention of bad breath occurs in ancient Egypt, where detailed recipes for toothpaste are prepared before the pyramids are built.

The Ebers Papyrus of 1550 BC describes the tablets for curing bad breath based on incense, cinnamon, myrrh and honey.

Hippocratic medicine advocated a mouthwash of red wine and spices to cure bad breath. Keep in mind that it is now believed that mouth rinses with alcohol exacerbate bad breath as you dry your mouth, which increases microbial growth.

The Hippocratic Corpus also describes a recipe based on marble dust for women suffering from bad breath. The ancient Roman physician Pliny wrote about methods to sweeten breathing.

Ancient Chinese emperors required visitors to chew cloves in front of an audience. The Talmud describes bad breath as a disability, which could be a reason for legal breakdown of a marriage license.

This traditional chewing stick is also called Miswak , especially used in Saudi Arabia, it is essentially like a natural toothbrush made of twigs.

During the Renaissance, Laurent Joubert , physician to King Henry III of France, states that bad breath is “caused by a dangerous miasma that falls on the lungs and through the heart, causing serious damage.”

In BG Jefferis and JL Nichols , “Reflections on Health” (1919), the following recipe is offered:

“One teaspoon of the following mixture after each meal: one ounce of soda chloride, one ounce of potash liqueur, one and a half ounce of soda phosphate and three ounces of water.”

At present, bad breath is one of the biggest social taboos.

The general population places great importance on the prevention of bad breath, illustrated by the $ 1 billion per year that consumers in the United States spend on deodorant-type (mental) mouthwashes, mints and related over-the-counter products.

Many of these practices are simply short-term attempts to mask the odor. Some authors have suggested that there is an evolutionary basis for worrying about bad breath.

An instinctive aversion to unpleasant odors can work to detect sources of food in poor condition and other substances potentially invective or harmful.

In general, it is believed that body odors play an important role in the selection of partners in humans, and the unpleasant odor can be a sign of illness and, therefore, a potentially unwise option for the couple.

Although the reports of bad breath are found in the first known medical writings, the social stigma has probably changed over time, possibly partly due to sociocultural factors that involve advertising pressures.

As a result, the negative psychosocial aspects of halitosis may have worsened, and psychiatric conditions such as halitophobia are probably more common than historically.

There have been rare reports of people committing suicide by halitosis, whether there is genuine halitosis or not.


The word halitosis is derived from the Latin word halitus, which means ‘breath’, and the Greek suffix osis meaning ‘sick’ or ‘a condition of’.

With modern consumerism, there has been a complex interaction of advertising pressures and the existing evolutionary aversion to bad odor.

Contrary to popular belief that Listerine coined the term halitosis, its origins date back to before the product existed, being coined by the physician Joseph William Howe in his 1874 book The Breath , and the diseases that give it a foul odor .

Although it only became commonly used in the 1920s when a marketing campaign promoted Listerine as a solution for “chronic halitosis”. The company was the first to manufacture mouthwashes in the United States.

Listerine was invented in the 19th century as a powerful surgical antiseptic. Later it was sold, in distilled form, as a floor cleaner and as a cure for gonorrhea.

But it was not a resounding success until the 1920s, when it was launched as a solution to “chronic halitosis,” a dark medical term for bad breath.

Listerine’s new ads showed young, helpless women and men, eager for marriage but disconnected by their partner’s rotten breath.


According to traditional medicine, chewing areca nut and betel leaf is a remedy for bad breath.

In South Asia, it was a custom to chew areca or betel nut and betel leaves among lovers because of the refreshing properties of the breath and stimulants of the mixture. Both the walnut and the leaf are gentle stimulants and can be addictive with repeated use.

Betel nut will also cause tooth decay and red or black tooth coloring when chewed.

However, betel leaf and betel mastication can cause premalignant lesions such as leukoplakia and submucosal fibrosis, and are recognized risk factors for oral and oropharyngeal squamous cell carcinoma (oral cancer).

Other traditional remedies for halitosis are guava leaves in Thailand, egg shells in China, parsley in Italy and urine mouthwash in certain European cultures.

Practitioners and alternative medicine providers sell a wide range of products that they say are beneficial for halitosis, including dietary supplements, vitamins and oral probiotics.

Halitosis is often claimed to be a symptom of the ” candida hypersensitivity syndrome ” or related diseases, and is said to be treatable with antifungal medications or alternative medications to treat fungal infections.


In 1996, the International Society for Respiratory Smell Research (ISBOR) was formed to promote multidisciplinary research on all aspects of breath odors.

The eighth international conference on smell of breath took place in 2009 in Dortmund, Germany, while the ninth was held in 2011 in Salvador de Bahia, Brazil.