Reasoning GP · Algorithm · 1-page summary
Halitosis (bad breath)
For: people with bad breath, genuine or perceived, in primary care. Not for: dry mouth as the main problem (dry mouth algorithm), mouth ulcers (mouth ulcers) or acute sore throat (sore throat).
Core rule: start with the mouth — most persistent halitosis is oral and dental. Halitosis alone is never a cancer or emergency criterion: the clinical features found on assessment (ulcer, lump, dysphagia, vomiting with confusion, airway) drive urgency.
0Stop — 999 or same day — airway, DKA, sepsis, liver, kidney
- Stridor, drooling or unable to swallow secretions → 999 Suspected quinsy or deep neck infection, severe systemic illness → Same-day ENT / ED
- Fruity breath with vomiting, Kussmaul breathing or confusion: glucose + ketones now → suspected DKA Immediate admission; 999 if confused, drowsy or Kussmaul.
- Musty breath with confusion (hepatic encephalopathy) → Same-day ED Acutely unwell with possible renal failure → Same-day (not on odour alone)
- Child with one-sided foul nasal discharge (foreign body) → Same-day ENT / ED; 999 if airway compromise.
1Triage by pattern — odour points, it does not diagnose
| Pattern | Likely source → action |
|---|---|
| Sulphurous, coated tongue, gums | Oral → hygiene + dentist |
| Worse through the nose | Sinonasal / tonsils → treat per local pathway |
| Fruity + unwell | DKA → glucose + ketones, block 0 |
| Faeculent + chronic cough | Lung abscess / bronchiectasis → respiratory exam + targeted imaging |
| Fishy or musty + systemic signs | Uraemia / liver → U&E or LFTs only if clinically suspected |
2Screen — features found on assessment
- Unexplained oral ulcer >3 weeks or persistent unexplained neck lump → consider Suspected cancer pathway (head and neck).
- Aged ≥45 with persistent unexplained hoarseness → consider Suspected cancer pathway (laryngeal). Trismus, one-sided ear pain with normal otoscopy, odynophagia → local head-and-neck pathway.
- Lump on lip or in mouth; red or red-and-white patch → Urgent dental assessment
- Dysphagia at any age (incl. regurgitating undigested food), or ≥55 with weight loss + upper abdominal pain, reflux or dyspepsia → Upper-GI suspected cancer pathway
- Unexplained haemoptysis aged ≥40 → Lung suspected cancer pathway; lung abscess unwell → Same-day
3Assess
☐ Has anyone else noticed it? ☐ Hygiene, last dental visit, dentures ☐ Dry-mouth drugs, smoking, alcohol, diet ☐ Mouth vs nose exhalation ☐ Tongue, gums, teeth, mucosa (ulcers, patches, lumps), tonsils, neck nodes; nose if indicated
Tests: only for a suspected cause — no routine endoscopy, H. pylori test, PPI trial, bloods, chest X-ray or imaging.
4Classify — only if the screen is negative
- Oral (commonest) — tongue coating, gum disease, caries, dentures, dry mouth → dentist.
- Physiological — morning, diet, fasting, smoking → advice only.
- ENT — rhinosinusitis, polyps, postnasal drip, tonsilloliths → treat; refer if persistent, unilateral, complicated or atypical.
- Extra-oral (rare) — lung, GI (GORD, Zenker's), metabolic, TMAU → only with compatible features.
- Pseudohalitosis / halitophobia — no malodour on oral + basic ENT assessment → explain, validate distress.
- Uncertain — persists after dental care → reassess oral, ENT and medicine causes.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Hygiene: fluoride toothpaste twice daily, interdental and gentle tongue cleaning, dentures out overnight. Stop smoking; alcohol ≤14 units/week.
- Dry mouth: review xerogenic drugs; water, sugar-free gum, saliva substitutes.
- Mouthwash: chlorhexidine only short-term in selected patients; CPC or zinc optional. Never instead of dental care.
- No antibiotics, empirical PPI or H. pylori test for halitosis alone; dyspepsia → NICE CG184 / local.
6Refer routinely
- Dentist (most cases); pain with swelling → prompt dental review.
- ENT: rhinosinusitis despite treatment, polyps or unilateral disease; tonsilloliths with disabling recurrent tonsillitis.
- No malodour + distress → NHS Talking Therapies; secondary mental health if severe impairment, fixed delusional conviction or risk.
- Persistent fish odour, normal oral/ENT exam, no diet or drug cause → metabolic medicine advice (TMAU).
7Never reassure by
- "Just bad breath" in a patient who is vomiting, confused or breathing deeply — check glucose and ketones.
- A coated tongue, without looking for ulcers, patches, lumps and neck nodes.
- Calling it reflux when there is dysphagia or regurgitation of undigested food.
- A PPI or mouthwash course in place of a dental assessment.
- Repeated tests or referrals when no malodour is found — validate and support.
- Assuming haemoptysis with foul breath is "just infection" in someone aged 40 or over.
8Safety-net — say it, then document it
999 “Call 999 if you have difficulty or noisy breathing, are drooling or cannot swallow saliva, or have fruity breath with vomiting, confusion, drowsiness or fast deep breathing.” Same day “Go to A&E today for severe one-sided throat pain with fever, difficulty opening your mouth or neck swelling. Contact us the same day for a new mouth ulcer, neck swelling, difficulty swallowing, coughing blood, yellow eyes or skin, or if your child has a smelly discharge from one nostril.”
Routine “See your dentist; come back if the smell persists after dental treatment.”
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Mouth, tonsils and neck examined
Genuine vs perceived judged; medicines reviewed
Dental review and hygiene advice arranged
Safety-net given; review if it persists after dental care
Summary of the full Reasoning GP halitosis algorithm, which holds the history, examination, causes, treatment detail and evidence. Sources: NICE NG12 (updated April 2026), CG184, NG30, NG79; local antimicrobial guidelines; ENT UK tonsillitis decision aid; British Dental Association. Clinical reference — follow local pathways and check doses: NICE/SPC, BNF.