Halitosis; Causes, Symptoms, Diagnosis, Treatment

Halitosis is a symptom in which a noticeably unpleasant odor is present on the breath. It can result in anxiety among those affected. It is also associated with depression and symptoms of obsessive-compulsive disorder. Concerns of bad breath may be divided into genuine and non-genuine cases. Of those who have genuine bad breath, about 85% of cases come from inside the mouth. The remaining cases are believed to be due to disorders in the nose, sinuses, throat, lungs, esophagus, or stomach. Rarely, bad breath can be due to an underlying medical condition such as liver failure or ketoacidosis.

Halitosis or oral malodor is an offensive odor originating from the oral cavity, leading to anxiety and psychosocial embarrassment. A patient with halitosis is most likely to contact primary care practitioner for the diagnosis and management. With proper diagnosis, identification of the etiology and timely referrals certain steps are taken to create a successful individualized therapeutic approach for each patient seeking assistance. It is significant to highlight the necessity of an interdisciplinary method for the treatment of halitosis to prevent misdiagnosis or unnecessary treatment. The literature on halitosis, especially with randomized clinical trials, is scarce and additional studies are required. This article succinctly focuses on the development of a systematic flow of events to come to the best management of the halitosis from the primary care practitioner’s point of view.

Classification of Halitosis

Two main classification schemes exist for bad breath, although neither is universally accepted.

The Miyazaki et al. classification was originally described in 1999 in a Japanese scientific publication and has since been adapted to reflect North American society, especially with regards halitophobia. The classification assumes three primary divisions of the halitosis symptom, namely genuine halitosis, pseudohalitosis, and halitophobia. This classification has been suggested to be most widely used, but it has been criticized because it is overly simplistic and is large of use only to dentists rather than other specialties.

Genuine halitosis

  • A. Physiologic halitosis
  • B. Pathologic halitosis > (i) Oral , (ii) Extra-oral
  • Pseudohalitosis
  • Halitophobia

The Tangerman and Winkel classification were suggested in Europe in 2002. This classification focuses only on those cases where there is genuine halitosis and has therefore been criticized for being less clinically useful for dentistry when compared to the Miyazaki et al. classification.

  • Intra-oral halitosis
  • Extra-oral halitosis

A. Bloodborne halitosis

  • (i) Systemic diseases
  • (ii) Metabolic diseases
  • (iii) Food
  • (iv) Medication

B. Non-blood borne halitosis

  • (i) Upper respiratory tract
  • (ii) Lower respiratory tract

The same authors also suggested that halitosis can be divided according to the character of the odor into 3 groups

  • “Sulfurous or fecal” caused by volatile sulfur compounds (VSC), most notably methyl mercaptan, hydrogen sulfide, and dimethyl sulfide.
  • “Fruity” caused by acetone, present in diabetes.
  • “Urine-like or ammoniacal” caused by ammonia, dimethylamine and trimethylamine (TMA), present in trimethylaminuria and uremia.

Based on the strengths and weaknesses of previous attempts at classification, a cause-based classification has been proposed

  • Type 0 (physiologic)
  • Type 1 (oral)
  • Type 2 (airway)
  • Type 3 (gastroesophageal)
  • Type 4 (blood-borne)
  • Type 5 (subjective)

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

Here are the Types of Smells Different Systemic Disease Halitosis

  • A cheesy smell usually indicates your bad breath has a nasal origin.
  • fruity smell may indicate uncontrolled diabetes due to increased
  • fishy smell may indicate kidney disease, as increased urea levels can cause a fishy smell such as in  (trimethylaminuria)
  • An acidic smell can be a sign of asthma or cystic fibrosis
  • The ascent of ammonia can indicate kidney problems
  • A sweet, musty odor may signal liver cirrhosis
  • A fecal odor may point to a bowel obstruction

Classification of Halitosis

In general, halitosis can be either primary or secondary:[]

  • Primary halitosis: Refers to respiration exhaled by the lungs[]
  • Secondary halitosis: Originates either in the mouth or upper airways.[]

Clinically, halitosis can be classified into three groups,[] namely

Real/Genuine halitosis
  • Physiologic halitosis: E.g. Morning halitosis
  • Pathologic halitosis:
    • Oral pathologic halitosis
    • Extra-oral pathologic halitosis
  • Pseudohalitosis – Complains of halitosis without the actual existence and can be treated by the dental practitioner by counseling and simple oral hygiene procedures.
  • Halitophobia – People with a fear of halitosis. Interestingly, this group of patients presents with symptoms of halitosis in the absence of objective oral malodor. This symptom may be attributable to a form of delusion or monosymptomatic hypochondriasis (self-oral malodor, halitophobia, phantom bad breath).[] This condition can be identified by the questionnaire method and require psychological investigation or support rather than a dental treatment.[]

Causes of Halitosis

Most bad breath starts in your mouth, and there are many possible causes. They include:

Bad breath starts at the back of the mouth, where sulfur-producing bacteria hide under the surface of the tongue. Poor oral hygiene, having food stuck between your teeth, gum disease and tooth decay all contribute to bad breath. Other, less common, causes include:

  • Food –  The breakdown of food particles in and around your teeth can increase bacteria and cause a foul odor. Eating certain foods, such as onions, garlic and spices, also can cause bad breath. After you digest these foods, they enter your bloodstream, are carried to your lungs and affect your breath.
  • Tobacco products –  Smoking causes its own unpleasant mouth odor. Smokers and oral tobacco users are also more likely to have gum disease, another source of bad breath.
  • Poor dental hygiene –  If you don’t brush and floss daily, food particles remain in your mouth, causing bad breath. A colorless, sticky film of bacteria (plaque) forms on your teeth. If not brushed away, plaque can irritate your gums and eventually form plaque-filled pockets between your teeth and gums (periodontitis). Your tongue also can trap bacteria that produce odors. Dentures that aren’t cleaned regularly or don’t fit properly can harbor odor-causing bacteria and food particles.
  • Dry mouth – Saliva helps cleanse your mouth, removing particles that cause bad odors. A condition called dry mouth or xerostomia (zeer–o-STOE-me-uh) can contribute to bad breath because the production of saliva is decreased. Dry mouth naturally occurs during sleep, leading to “morning breath,” and it worsens if you sleep with your mouth open. Chronic dry mouth can be caused by a problem with your salivary glands and some diseases.
  • Medications –  Some medications can indirectly produce bad breath by contributing to dry mouth. Others can be broken down in the body to release chemicals that can be carried on your breath. Systemic diseases – There are a few systemic (non-oral) medical conditions that may cause foul breath odor, but these are infrequent in the general population. Such conditions are
    1. Fetor hepaticus – an example of a rare type of bad breath caused by chronic liver failure.
    2. Lower respiratory tract infections (bronchial and lung infections).
    3. Kidney infections and kidney failure.
    4. Carcinoma.
    5. Trimethylaminuria (“fish odor syndrome”).
    6. Diabetes mellitus.
    7. Metabolic conditions, e.g. resulting in elevated blood dimethyl sulfide.

    Individuals afflicted by the above conditions often show additional, more diagnostically conclusive symptoms than bad breath alone.

  • Infections in your mouth – Bad breath can be caused by surgical wounds after oral surgery, such as tooth removal, or as a result of tooth decay, gum disease or mouth sores.
  • Dental hygiene –  Brushing and flossing ensure the removal of small particles of food that can build up and slowly break down, producing odor. A film of bacteria called plaque builds up if brushing is not regular. This plaque can irritate the gums and cause inflammation between the teeth and gums called periodontitis. Dentures that are not cleaned regularly or properly can also harbor bacteria that cause halitosis.
  • Crash diets – Fasting and low-carbohydrate eating programs can produce halitosis. This is due to the breakdown of fats producing chemicals called ketones. These ketones have a strong aroma.
  • Drugs – Certain medications can reduce saliva and, therefore, increase odors. Other drugs can produce odors as they break down and release chemicals in the breath. Examples include nitrates used to treat angina, some chemotherapy chemicals, and some tranquilizers, such as phenothiazines. Individuals who take vitamin supplements in large doses can also be prone to bad breath.
  • Mouth, nose, and throat conditions –  Sometimes, small, bacteria-covered stones can form on the tonsils at the back of the throat and produce odor. Also, infections or inflammation in the nose, throat, or sinuses can cause halitosis.
  • Foreign body –  Bad breath can be caused if they have a foreign body lodged in their nasal cavity, especially in children.
  • Other mouths, nose and throat conditions – Bad breath can occasionally stem from small stones that form in the tonsils and are covered with bacteria that produce odor. Infections or chronic inflammation in the nose, sinuses or throat, which can contribute to postnasal drip, also can cause bad breath.
  • Other causes – Diseases, such as some cancers, and conditions such as metabolic disorders, can cause a distinctive breath odor as a result of the chemicals they produce. Chronic reflux of stomach acids (gastroesophageal reflux disease, or GERD) can be associated with bad breath. Bad breath in young children can be caused by a foreign body, such as a piece of food, lodged in a nostril.
  • Ketoacidosis – When the insulin levels of a person with diabetes are very low, their bodies can no longer use sugar and begin to use fat stores instead. When fat is broken down, ketones are produced and build up. Ketones can be poisonous when found in large numbers and produce a distinctive and unpleasant breath odor. Ketoacidosis is a serious and potentially life-threatening condition.
  • Bowel obstruction – Breath can smell like feces if there has been a prolonged period of vomiting, especially if a bowel obstruction is present.
  • Bronchiectasis – This is a long-term condition in which airways become wider than normal, allowing for a build-up of mucus that leads to bad breath.
  • Aspiration pneumonia – A swelling or infection in the lungs or airways due to inhaling vomit, saliva, food, or liquids.
  • Gastrointestinal problems – where stomach bacteria produces odor
  • Crash dieting – where your body breaks down fat, which releases foul-smelling acids

Other Causes of Halitosis

Other less common reported causes from within the mouth include

  • Deep carious lesions (dental decay) – which cause localized food impaction and stagnation
  • Recent dental extraction sockets – fill with a blood clot, and provide an ideal habitat for bacterial proliferation
  • Interdental food packing – (food getting pushed down between teeth) – this can be caused by missing teeth, tilted, spaced or crowded teeth, or poorly contoured approximal dental fillings. Food debris becomes trapped, undergoes slow bacterial putrefaction and release of malodorous volatiles. Food packing can also cause a localized periodontal reaction, characterized by dental pain that is relieved by cleaning the area of food packing with interdental brush or floss.
  • Acrylic dentures (plastic false teeth) – inadequate denture hygiene practices such as failing to clean and remove the prosthesis each night, may cause a malodor from the plastic itself or from the mouth as microbiota responds to the altered environment. The plastic is actually porous, and the fitting surface is usually irregular, sculpted to fit the edentulous oral anatomy. These factors predispose to bacterial and yeast retention, which is accompanied by a typical smell.
  • Oral infections
  • Oral ulceration
  • Fasting
  • Stress/anxiety
  • Menstrual cycle – at mid-cycle and during menstruation, increased breath VSC were reported in women.
  • Smoking – Smoking is linked with 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 dental decay to premalignant lesions and even oral cancer.
  • Alcohol
  • Volatile foods  – e.g. onion, garlic, durian, cabbage, cauliflower, and radish. Volatile foodstuffs may leave malodorous residues in the mouth, which are the subject to bacterial putrefaction and VSC release. However, volatile foodstuffs may also cause halitosis via the blood borne halitosis mechanism.

Common causes of the symptom of oral malodor (halitosis)

Oral disease

  • Food impaction
  • Acute necrotizing ulcerative gingivitis
  • Acute gingivitis
  • Adult and aggressive periodontitis
  • Pericoronitis
  • Dry socket
  • Xerostomia
  • Oral ulceration
  • Oral malignancy

Respiratory disease

  • Foreign body
  • Sinusitis
  • Tonsillitis
  • Malignancy
  • Bronchiectasis

Volatile foodstuffs

  • Garlic
  • Onions
  • Spiced foods

Possible systemic causes of oral malodor

  • Acute febrile illness
  • Respiratory tract infection (usually upper)
  • Helicobacter pylori infection (?)
  • Pharyngo-oesophageal diverticulum
  • Gastro-oesophageal reflux disease
  • Pyloric stenosis or duodenal obstruction
  • Hepatic failure (fetor hepaticus)
  • Renal failure (end stage)
  • Diabetic ketoacidosis
  • Leukaemias
  • Trimethylaminuria
  • Hypermethioninaemia
  • Menstruation (menstrual breath)

Examples of drugs that may cause oral malodor

  • Alcohol
  • Tobacco
  • Betel
  • Solvent misuse
  • Chloral hydrate
  • Nitrites and nitrates
  • Dimethyl sulphoxide
  • Disulphiram
  • Some cytotoxic agents
  • Phenothiazines
  • Amphetamines

Odoriferous components that give rise to oral malodor

Volatile sulphur compounds

  • Methyl mercaptan
  • Hydrogen sulphide
  • Dimethyl sulphide


  • Putrescine
  • Cadaverine

Short chain fatty acids

  • Butyric acid
  • Valeric acid
  • Propionic acid

Box 5: Clinical assessment of oral malodour


  • Intensity—the organoleptic method
    • Smelling expelled air of mouth and nose separately
    • Easy to do, requires no clinical training
  • Quality—the hedonic method
    • Rarely clinically applicable
    • Requires well trained clinical judges


  • Detection of sulfides with appropriate monitor—simple, but may fail to detect oral malodor caused by non-sulfide components
  • Gas chromatography—not applicable for routine clinical practice
  • Bacterial detection (such as benzoyl-arginine-naphthylamide test, polymerase chain reaction, dark field microscopy)—not applicable for routine clinical practice

Different medical conditions, impart different odor on the patient’s breath.

  • Diabetes – Fruity or citrusy breath
  • Asthma or cystic fibrosis – Acidic breath
  • Kidney problem – Scent of ammonia
  • Hepatic cirrhosis – Musty or mousey odor[]
  • Trimethylaminuria – Foul fishy odor
  • Nasal malodor – Slightly cheesy character
  • Bowel obstruction – Fecal odor.[]

Ketoacidosis (uncontrolled diabetes can produce diabetic ketoacidosis) – Sweet fruity and/or acetone breath or rotten apple breath.

Excessive ketone production can also result from dieting. Low carbohydrate diet, burns the body’s fat content for energy production and produces excessive ketones. Stopping the dieting, changing the diet with high carbohydrate content and low-fat content, drinking extra water to flush out the body prevents ketone breath.[]

Symptoms 0f Bad Breath

Other signs and symptoms of bad breath include

  • unpleasant or sour taste or changes in taste,
  • dry mouth, and
  • a coating on the tongue.
  • The coating on the tongue (white, yellow or brown)
  • Adverse reactions from people around you (cover their nose, turn their head, offer gum or mints)
  • Morning breath
  • Brushing and flossing do little for the odor
  • Mouthwashes are only temporary
  • Constant bad taste in the mouth
  • Dry mouth, thick saliva
  • Post-nasal drip

Diagnosis of Bad Breath

They include the following

  • Halimeter – This detects low levels of sulfur.
  • BANA test – This measures levels of a specific enzyme produced by halitosis-causing bacteria.
  • Beta-galactosidase test – Levels of the enzyme beta-galactosidase have been found to correlate with mouth odor.
  • Gas chromatography – portable machines, such as the OralChroma, are currently being introduced. This technology is specifically designed to digitally measure molecular levels of the three major VSCs in a sample of mouth air (hydrogen sulfide, methyl mercaptan, and dimethyl sulfide). It is accurate in measuring the sulfur components of the breath and produces visual results in graph form via a computer interface.
  • β-galactosidase test – salivary levels of this enzyme were found to be correlated with oral malodor.

Treatment of oral malodor

  • Investigate and manage possible systemic (non-oral) source if organoleptic method detects malodor from both mouth and nose
  • Improve oral hygiene by professional and patient-administered tooth cleaning
  • Regular atraumatic tongue cleaning
  • Regular use of antimicrobial toothpaste and mouthwashes, such as
    • Chlorhexidine gluconate
    • Cetylpyridinium (not available in UK)
    • Oil-water rinse
    • Triclosan/copolymer/sodium fluoride toothpaste
  • Regular clinical review to ensure maintenance of effective oral hygiene
  • Halitophobia warrants referral to a clinical psychologist
  • BANA test – The BANA test is practical for chair-side usage. It is a test strip which composed of benzoyl-DL-arginine-a-naphthylamide and detects short-chain fatty acids and proteolytic obligate gram-negative anaerobes, which hydrolyze the synthetic trypsin substrate and cause halitosis. It detects especially Treponema denticolaP. gingivalis, and T. forsythensis that associated with periodontal disease. By using the BANA test, we can detect not only halitosis but also periodontal risk assessment.[,,]
  • Quantifying β-galactosidase activity – Deglycosylation is the removed link of glycosyl groups from glycoproteins. Deglycosylation of glycoproteins is the initial step in oral malodor production.[] By deglycosylation of glycoproteins, proteolytic bacteria degrade proteins which are especially salivary glycoproteins and cause halitosis. Proteolysis of glycoprotein depends on the initial removal of the carbohydrate side-chains which are O- and N-linked carbohydrates. β-Galactosidase is one of the important enzymes which are responsible for the removal of both O- and N-linked carbohydrate side-chains.[,]
  • Salivary incubation test – The salivary incubation is one of the assessment methods to measure halitosis indirectly. The first time, Marc Quirynen et al. carried out a study to evaluate salivary incubation and halitosis. To measure halitosis with the salivary incubation test, saliva was collected in a glass tube and then incubating the tube at 37°C in an anaerobic chamber under an atmosphere of 80% nitrogen, 10% carbon dioxide, and 10% hydrogen for 3-6 h. After incubation, an examiner evaluates the odor. Although this method has some similarities with the organoleptic measurements, it has some advantages over them. The most important advantage is that the salivary incubation test has much less influenced by external parameters such as smoking, drinking coffee, eating garlic, onion, spicy food, and scented cosmetics.

Treatment of Bad Breath

  • Mouth rinses and toothpaste – If your bad breath is due to a buildup of bacteria (plaque) on your teeth, your dentist may recommend a mouth rinse that kills the bacteria. Your dentist may also recommend a toothpaste that contains an antibacterial agent to kill the bacteria that cause plaque buildup.
  • Treatment of dental disease – If you have gum disease, you may be referred to a gum specialist (periodontist). Gum disease can cause gums to pull away from your teeth, leaving deep pockets that fill with odor-causing bacteria. Sometimes only professional cleaning removes these bacteria. Your dentist might also recommend replacing faulty tooth restorations, a breeding ground for bacteria.

Efforts may include physical or chemical means to decrease the numbers of bacteria, products to mask the smell, or chemicals to alter the odor creating molecules. It is recommended that in those who use tobacco products stop. Evidence does not support the benefit of dietary changes or chewing gum.

Mechanical measures

  • Brushing the teeth may help. While there is evidence of tentative benefit from tongue cleaning it is insufficient to draw clear conclusions. A 2006 Cochrane review found tentative evidence that it might decrease levels of odor molecules. Flossing may be useful.


  • A 2008 systematic review found that antibacterial mouth rinses may help. Mouthwashes often contain antibacterial agents including cetylpyridinium chloride, chlorhexidine, zinc gluconate, essential oils, hydrogen peroxide, and chlorine dioxide. Cetylpyridinium chloride and chlorhexidine can temporarily stain teeth.

Underlying disease

  • If gum disease and cavities are present, it is recommended that these be treated.
  • If diseases outside of the mouth are believed to be contributing to the problem, treatment may result in improvements.
  • Counseling may be useful in those who falsely believe that they have bad breath.

Natural Solutions For Bad Breath

  • Worries about bad breath from time to time especially after a spicy meal or a cup of coffee. In fact, about 9 percent of people reported having bad breath within the past 6 months, according to the Centers for Disease Control and Prevention (CDC).
  • For some people, bad breath is persistent and experts agree it’s likely a symptom of a more serious health problem.
  • Coffee, alcohol, onions, and garlic – can all cause bad breath, as can low-carb diets like Paleo and Atkins. Yet experts agree the number one reason people suffer from chronic bad breath is poor oral hygiene. Millions of bacteria live below the gumline and on the back of the tongue. If they’re not regularly and properly cleaned, the bacteria will eat off the proteins and food particles in the mouth and release gases known as volatile sulfur compounds.
  • See your dentist – It’s important to find out where the odor is coming from and whether or not it ’s due to a medical condition or a dental problem. Since bacteria can live in the deep pockets below the gum line, your dentist can make sure you’re brushing and flossing properly.
  • Brush – It’s a no-brainer, but brushing after meals or at least twice a day will keep bad breath at bay. It’s also important to be methodical about brushing and make sure you’re getting all of the surfaces of your teeth and gums. “Even if you have one tooth that you miss every time, that can cause some pretty nasty breath,” said Dr. Joseph Banker, founder of Creative Dental Care in Westfield, New Jersey.
  • Floss – An ultrasonic toothbrush is a good choice, but the best way to get below the gum line and in-between teeth is to floss right after you brush, every time. “If you leave food there constantly, it just sits and rots—and that smells,” Banker said.
  • Drink up – If you’re not drinking enough water, your salivary flow decreases, which can cause breath to be more concentrated. Always carry water with you and be sure to drink throughout the day.
  • Be picky about mouthwash – Mouthwash does a great job killing the bacteria that cause bad breath, but if it has a high alcohol content, it can be too drying and actually cause bacteria to grow, Goldberg said. Look for an alcohol-free mouthwash, and ingredients like menthol, eucalyptol or thymol instead. Also, wait 15 minutes after brushing to rinse so the mouthwash will be effective.
  • Use a tongue scraper – Brushing your tongue only gets to the surface, but a tongue scraper used every time you brush is much more effective. “The tongue harbors tons of bacteria and it’s a huge surface area in the mouth,” Banker said.
  • Have a glass of wine – A recent study in the Journal of Agricultural and Food Chemistry finds that drinking red wine in moderation can inhibit the growth of bacteria. Be sure to rinse with water afterward to prevent staining.
  • Bite into an apple – Fiber-rich fruits and vegetables that require a lot of chewing help to clean out the teeth and the vitamin C will kill bacteria.
  • Chew gum – Chewing sugarless gum throughout the day can help to clean out food particles in the teeth and keep the mouth moist.
  • Drink tea – Swap out your afternoon coffee for a cup of green or black tea instead. Both contain polyphenols, which prevent the growth of bacteria.
  • Take probiotics – A probiotic supplement may help to cut down on candida yeast that lives on the surface of the tongue, Goldberg said.

Here are some tips for getting rid of bad breath

  • Brush your teeth at least 2 times a day and floss once daily.
  • Gently clean your tongue before bedtime by scraping with a plastic tongue cleaner or brushing gently.
  • Prevent hunger breath by eating regularly and avoiding fasting or skipping meals.
  • Ask your dentist to recommend a specific cleaning system that can help clean your mouth more thoroughly than with just regular brushing.
  • Keep your nose and sinuses clean.
  • Stimulate saliva flow with acidic fruits such as oranges and lemons or sugarless gums and candy.
  • Eat more fibrous foods. Chew fibrous vegetables such as raw carrots and celery to stimulate saliva flow.
  • Drink at least 8 glasses of water daily to keep your mouth moist and to help rinse away odor-forming bacteria.
  • Decrease alcohol and coffee intake.
  • Ask your doctor or pharmacist whether your medications are causing problems of dry mouth that may be leading to bad breath.
  • Rinse and gargle with an effective mouthwash.


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