Bad breath is medically known as Halitosis, Fetor oris or Fetor exore is a condition in which constant foul smell is present in the air exhaled through mouth. Bad Breath/Halitosis is very rarely noticed by patient himself, who is suffering from it. Bad Breath is most often noticed by the companions of the patient, when the patient speaks or laughs. Bad breath may get the patient suffering from it in a very embarrassing situation. Due to this embarrassing position persons having bad breath hesitate to talk & laugh freely, feel unconfident and may have low self esteem. Thus bad breath/halitosis affects person’s personal, social as well as professional life.

Causes of Bad Breath/Halitosis

Most of the patients suffering from bad breath/halitosis often do not know what is causing bad breath. Some of them wonder that they have bad breath even after getting their teeth professionally cleaned and maintaining good oral hygiene. So, to eliminate bad breath one should know the cause of bad breath before approaching for any treatment. Bad breath can be due to oral, respiratory, gastrointestinal problems, diabetes, renal problems, and liver failure.

Oral Causes

Dental Caries: Dental caries  causes bad breath/Halitosis. Decay of teeth or cavities (Caries) is caused by dissolution of hard tissues of teeth by the acid produced by bacteria. It mostly occurs due to excessive sugar consumption and not maintaining proper oral hygiene. Bacteria proliferate in great amounts in cavities created by them. Especially anaerobic bacteria get proper conditions to proliferate in the deep cavities due to less oxygen supply. These anaerobic bacteria produce substances having foul odor such as indole, skatole, polyamines and volatile sulphur compounds (VSCs) such as hydrogen sulphide, methyl mercaptan and dimethyl sulphide which cause bad breath.

Periodontal Diseases


Periodontal diseases also cause bad breath/halitosis. These are the diseases, which  affect the tissues surrounding teeth. Gingivitis, periodontitis, periodontosis, periodontal abscess are these diseases and these often causes bad breath  

These diseases cause bad breath again due to proliferation of anaerobic bacteria in the deep periodontal pockets and production of foul smelling substances by them.

Food Impaction: Food impaction also causes bad breath/halitosis. This is a condition in which food gets trapped between spaces in the teeth due to excessive spacing between teeth, cavities/caries in teeth, improper restorations(fillings), ill fitting crowns and bridges. Breakdown of this food material by microbes causes bad breath. Especially proteins present in food which are broken down into amino acids which are further broken down into sulphur containing foul smelling compounds by the oral bacteria leading to bad breath.

Xerostomia/Dry Mouth: Dry Mouth can lead to bad breath. It is condition in which salivary flow in the mouth decreases. It may due to:

  1. Conditions affecting salivary glands such as infections (mumps), autoimmune conditions (Sjogren’s syndrome), obstruction of salivary gland duct by stones (sialolithiasis)

  2. Certain systemic conditions such as dehydration, diabetes, certain medications such as anti-depressants, anti-histaminic and amphetamines.

  3. Transient Xerostomia occurs during sleep and after speaking for a long time such as after giving lectures

  4. Reduced salivary flow causes bad breath/halitosis because it interrupts following functions of saliva

  5. Saliva helps in washing away of secretions and bacteria that cause foul smell.

  6. It contains an antibacterial enzyme lysozyme which causes destruction of bacteria.

  7. It reduces plaque formation by neutralizing and diluting the bacterial products.

  8. It decreases caries formation by acting as a buffer to acid produced by bacteria causing dissolution of tooth and also by rematerializing the defect produced by these bacteria.

Pericoronitis: Inflammation of tissues around erupting or impacted third molar tooth results in formation of pericoronal flap which harbors numerous microbes. It also leads to food impaction under flap furthercontributing to microbial growth. Putrefaction of food material by the bacteria produces foul smelling substances which ultimately lead to bad breath/halitosis

Tooth Abscess: Collection of pus in the gingiva (gingival abscess), periodontal pocket (periodontal abscess) or beneath the root (periapical abscess) also causes halitosis due to presence of putrefying bacteria in the pus.


Poor oral hygiene is major source of bad breath/halitosis. If proper oral hygiene is not maintained it leads to plaque formation which causes dental caries, periodontal problems and infections leading to halitosis. Improper cleaning of tongue leads to whitish coating on the surface of tongue which consists of substances producing foul smell.

Usually halitosis is from the back portion of the tongue because front portion gets self cleaned by rubbing with hard palate while speaking and eating while back portion of tongue comes in contact with soft palate while functioning so, doesn’t get clean properly.


Tonsillitis: Infection and inflammation of tonsils lodges anaerobic bacteria in the crypts of tonsils which produce foul smelling substances and hence bad breath. Tonsillolith (calcified matter in the tonsil) exhibit very foul smell if they are released.

Dentures and Removable Orthodontic Appliances: If you are using dentures or removable orthodontic appliances then these may act as source of halitosis if not cleaned properly because of accumulation of food material beneath them which promotes growth of microbes causing bad breath.

So, the root cause of all oral conditions producing halitosis is bacteria producing foul smelling substances. Now the question arises From where do these bacteria come?
Certain bacteria are normal inhabitants of oral cavity which constitute normal flora and they do no harm. But if proper oral hygiene is not maintained, number and activities of these bacteria increase and conditions are created for the growth of more harmful bacteria with everlasting names like Peptostreptococcus anaerobius, Fusobacterium periodonticum, Stomatococcus mucilaginous which cause halitosis.

Respiratory Conditions (Conditions Affecting Airways)

Sinusitis: Due to infection and inflammation of sinuses, nasal secretions may fall on the posterior (back) surface of tongue which further acts as a source of nutrition for bacteria and thus causes their proliferation. So, patients suffering from sinusitis have bad breath due to following reasons

1.   Foul smelling secretions falling on the back surface of tongue.

2.   These secretions further promote the growth of anaerobic oral bacteria by acting as a source of nutrition for these bacteria.

3.   Patients having nasal blockage breathe from mouth which leads to dryness of mouth further aggravating halitosis.

4.   Sinusitis patients are prescribed medications such as anti histaminics (anti allergic), antibiotics which cause Xerostomia or Bad Breath.

Nasal polyp and any foreign body obstruction in the nasal passage forces the person to breathe through mouth, causes dryness of mouth and hence leading to bad breath.
Certain respiratory diseases like Bronchitis and Pneumonia also cause halitosis due to presence of foul smelling substances in the air exhaled by lungs.

Gastrointestinal Problems (Conditions Affecting Stomach)

  1. Fasting for prolonged period and less intake of fats & carbohydrates causes excessive breakdown of proteins into amino acids which are further broken down into volatile sulphur compounds and they are distributed in the whole body. When they reach lungs they are exhaled in the expired air causing halitosis. 

  2. Certain diseases like gastritis, food reflux, food stagnation also cause bad breath. These conditions are to be treated with proper medical advice. 

Miscellaneous Conditions Causing Bad Breath

  1. Fetor hepaticus in liver failure

  2. Renal failure

  3. Diabetes mellitus results in acetone breath

  4. Fish odour syndrome: It is disorder in which an enzyme which breaks down trim ethylamine is not present in the body of patient due to which it is not degraded and released in sweat, urine and breath causing strong fishy odour. 


Leave Comment


  • dr ritz

    dr ritz 23 - October - 2011, at 22:50 PM

  • Melba, Intake of vitamins doesn’t cause bad breath but if the vitamins are not digested properly because of bad digestion, then it can lead to bad breath. Bad breath can be because of poor oral hygiene, periodontal problems or cavities in the teeth, not cleaning the tongue or can be because of some of the systemic problems like lesser of saliva in the mouth or respiratory or gastric disorders. It is not a disease but is a symptom of disease. You can visit your dentist and or medical doctor to get the reason of bad breath diagnosed and treated. Brush and floss regularly and if there are any cavities or gum problems present, then get treatment done for it. Take more of fluids and even if the bad breath persists then consult your physician.

  • melba jenkins

    melba jenkins 22 - October - 2011, at 09:06 AM

  • I took a large amount of vitamin A for eight to ten years. Could that cause bad breath?

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