Bad Breath

This common symptom is usually caused by poor dental hygiene. As a presenting complaint it is seen far more often by dentists than GPs. It may be detected by a doctor examining a patient for an unrelated complaint, and rarely but significantly can herald serious pathology.

Published: 2nd August 2022 | Updated: 15th August 2022

Differential diagnosis

Common Diagnoses

  • Poor Dental Hygiene
  • Heavy Smoking
  • Gingivitis (Including Acute Necrotising Ulcerative Gingivitis [ANUG], Acute and Chronic Gingivitis)
  • Excess Alcohol Intake (Acute and Chronic)
  • Discharging Dental Abscess

Occasional Diagnoses

  • Ketohalitosis of Starvation: Especially in People Using High-Protein, High-Fat, Low-Carbohydrate Weight Reduction Diet Regimens (and Pre-Operatively Starved Patients)
  • Drugs, e.g. Disulfiram
  • Acute or Chronic Sinusitis
  • Subjectively Perceived (Non-Existent) Halitosis (Sometimes a Form of somatisation)
  • GORD or Acute Gastroenteritis with Reflux of Gas

Rare Diagnoses

  • Bronchiectasis
  • Liver Failure: Hepatic Foetor is Said to Smell Like a Freshly Opened Corpse; This is Due to Mercaptans in Expired Air
  • True Delusional Subjective Halitosis as Part of Psychiatric Condition, e.g. Severe Depression with Nihilism, Psychotic Illnesses
  • Rare Oral or Nasal Conditions (e.g. Pyogenic Granuloma, Discharging Sinus from Abscess)

Ready reckoner

Key distinguishing features of the most common diagnoses

Poor Dental HygieneHeavy SmokingGingivitisExcess AlcoholDental Abscess
Painful Face/JawNoNoPossibleNoYes
Bleeding GumsPossibleNoYesPossiblePossible
Facial SwellingNoNoNoNoYes
Dental StainingYesPossiblePossibleNoPossible
Intoxication/Stigmata of Chronic Alcohol AbuseNoNoNoYesNo

Possible investigations

  • It is unlikely that the GP will initiate any investigations other than LFT if alcohol is a likely aetiology, or liver failure is suspected. CXR may be helpful if bronchiectasis is a possibility. Dentists may carry out the following investigations.
  • Plaque and bleeding indexes: For oral hygiene.
  • Basic periodontal examination: Measurement of pocket depth between gums and teeth carried out with a specially marked probe.
  • Oral pantomograph X-ray to investigate general state of teeth.

Top Tips

  • The vast majority of cases will involve oral hygiene. Be certain to exclude this, and other physical causes, before deciding that the halitosis is entirely subjective. As with other forms of somatisation, active management – with a psychiatric referral if necessary – is preferable to sending the patient away, only to return to make more appointments.
  • If no obvious oral cause is found initially, extend the history and examination to include the respiratory and gastrointestinal systems.
  • ANUG is a ‘spot diagnosis’ – the stench usually precedes the patient by some distance.

Red Flags

  • In the absence of an obvious cause, do not neglect to examine the head and neck including the buccal cavity and nasal airway. Failure to do so could mean that a serious local cause is missed.
  • Do not overlook alcohol abuse as a possible underlying cause.
  • If the impact of the symptom seems out of all proportion to any objective sign of a problem, consider depression.
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Website disclaimer

Pulse Reference is based on the best-selling book Symptom Sorter.

The experts behind Pulse Reference are Dr Keith Hopcroft who is the co-author of Symptom Sorter, a GP in Essex and Pulse’s editorial advisor and Dr Poppy Freeman, a GP in Camden and also a clinical advisor to Pulse.

This website is for clinical guidance only and cannot give definitive diagnostic information. Practitioners should work within the limits of their individual professional practice, seek guidance when necessary and refer appropriately.