Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Chronic cough differential diagnosis
Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Acute deterioration within chronic cough
Haemoptysis threatening the airway, hypoxaemia, severe respiratory distress, suspected inhaled foreign body, sepsis or weight-losing tuberculosis requires urgent assessment despite the cough's duration.
Action: Stabilise airway, breathing and circulation, give oxygen, isolate appropriately when transmissible infection is possible and involve paediatrics. Use the foreign-body, haemoptysis, sepsis or TB pathway immediately; take targeted cultures and imaging without delaying emergency treatment. Do not attribute new physiological compromise to a benign chronic or habit cough.
Overview
Assess cough persisting beyond the expected acute period by wet or dry quality, onset, age and red flags; identify foreign body, suppurative lung disease and aspiration; use targeted radiography and spirometry; and avoid indiscriminate antibiotics, acid suppression or asthma treatment.
Cough protects the airway. Acute viral epithelial irritation can persist for weeks, but daily cough beyond expected recovery may signal retained secretion, ongoing inflammation, aspiration or a hypersensitive reflex.
Wet quality directs attention to endobronchial secretions. Protracted bacterial bronchitis, bronchiectasis, CF, ciliary disease, foreign body and aspiration form a linked spectrum that requires active differentiation.
Dry cough can reflect post-viral hypersensitivity, asthma, upper-airway irritation, environmental exposure or a tic. Timing alone rarely identifies the cause.
History begins at the first day, not the clinic date. Abrupt onset is a foreign-body clue; neonatal onset suggests congenital or aspiration disease; repetitive paroxysms suggest pertussis.
Examination includes growth, oxygenation, clubbing, ENT, chest symmetry and crackles, cardiac signs and neurodevelopment. Observe swallowing when feeds trigger cough.
Practice
Two practice questions
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Question 1 of 2
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Paediatrics and child healthOriginal SBA
Persistent wet cough
A 4-year-old has an isolated daily wet cough for 5 weeks, normal growth and no specific red flag. What is an appropriate next management step after radiograph and assessment?
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Chest radiography detects focal collapse, consolidation and gross structural change but early bronchiectasis and radiolucent objects can be invisible.
Spirometry assesses obstruction and reversibility. Normal results do not exclude intermittent asthma, but repeated normal objective testing weakens an asthma explanation for isolated cough.
PBB is a clinical treatment-response diagnosis. Antibiotic choice covers common airway bacteria; incomplete response requires confirmation of dose and adherence and a broader disease search.
CT uses child-optimised protocols only when structural information will change care. Bronchoscopy retrieves foreign bodies, samples lower-airway organisms and evaluates anatomy in selected cases.
Reassurance is an active outcome after a normal assessment: explain expected duration, remove irritants, avoid suppressants and set a date for reassessment.
Families can experience substantial sleep and school disruption even when physiology is safe. Validate burden while avoiding unsupported medicine trials.
Multidisciplinary care may include respiratory, ENT, speech and language therapy, immunology, physiotherapy and psychology according to the cough pathway.
Key points
Definitions vary: paediatric respiratory pathways commonly investigate daily cough beyond 4 weeks, while traditional BTS terminology calls more than 8 weeks chronic. Use trajectory and red flags rather than waiting for a label.
First branch is wet versus dry. A wet cough indicates airway secretion even when a child swallows sputum; parent-recorded audio or video can improve description.
First-line assessment is detailed history, examination, chest radiograph and spirometry with bronchodilator response when age and ability permit.
Ask onset, choking, cough-free intervals, nights, exercise, meals, position, triggers, whoop, vomiting, infections, medicines, smoke or vaping, travel and family history.
A normal chest radiograph does not exclude foreign body, bronchiectasis or aspiration. Red flags determine specialist CT, bronchoscopy, sweat test, ciliary, immune or swallow testing.
Protracted bacterial bronchitis is an isolated chronic wet cough without alternative pointers that resolves after an appropriate 2-week antibiotic, usually co-amoxiclav. Obtain culture when feasible and review at the end.
If wet cough fails to resolve after 2–4 weeks of appropriate treatment or recurs repeatedly, investigate bronchiectasis, foreign body, immune deficiency, CF and primary ciliary dyskinesia rather than repeating courses indefinitely.
Aetiology
01
Persistent airway infection
Protracted bacterial bronchitis and bronchiectasis retain infected secretions that stimulate a daily wet cough. within the child-specific clinical phenotype.
02
Variable airway inflammation
Asthma and eosinophilic disease produce episodic dry cough with wheeze, triggers and reversible airflow change. within the child-specific clinical phenotype.
03
Mechanical or aspiration cause
Foreign body, swallowing dysfunction, airway malacia and congenital lesions repeatedly irritate or obstruct the airway. within the child-specific clinical phenotype.
04
Post-infectious neural sensitivity
Viral or pertussis injury can leave a hypersensitive cough reflex after active infection has resolved. within the child-specific clinical phenotype.
Pathophysiology
1
Secretion receptor stimulation
Mucus and neutrophilic inflammation activate airway sensory nerves and produce the audible wet cough phenotype. during progression of the respiratory disorder.
2
Bronchial hyperresponsiveness
Inflamed asthmatic airways constrict to triggers, creating variable obstruction, wheeze and cough. during progression of the respiratory disorder.
3
Repeated aspiration injury
Food, liquid or refluxate entering the airway causes chemical inflammation, infection and progressive structural damage. during progression of the respiratory disorder.
4
Cough hypersensitivity and learning
After illness, heightened sensory gain and tic reinforcement can sustain cough without ongoing lower-airway disease. during progression of the respiratory disorder.
Clinical features and red flags
Cough quality
Clarify wet, dry, barking, paroxysmal or honking sound using caregiver recordings when clinic cough is absent.
Onset and timing
Establish abrupt choking, neonatal onset, infection, nights, exercise, meals, position and cough-free periods.
01First-line: chest radiographFirst stepFirst line
Why
Identify focal collapse, infection, gross structural disease or cardiac enlargement.
Interpretation and limitations
A normal film narrows but does not exclude foreign body, aspiration or bronchiectasis.
02First-line when able: spirometry with reversibilityFirst line
Why
Assess obstructive physiology and variable bronchodilator response.
Interpretation and limitations
Reversibility supports asthma in the correct phenotype; normal testing weakens but may not exclude intermittent disease.
03Airway culture
Why
Identify bacteria in chronic wet cough or exacerbation before antibiotics when possible.
Interpretation and limitations
Interpret sputum, cough swab or lavage quality and repeated organisms with the respiratory team.
04Thin-section CT
Why
Confirm bronchiectasis or define persistent focal structural disease.
Interpretation and limitations
Use specialist, child-optimised imaging when wet cough, clubbing, abnormal film or treatment failure justifies radiation.
05
Differential diagnosis
01
Protracted bacterial bronchitis
Chronic isolated wet cough resolving after appropriate 2-week antibiotic supports PBB, with recurrence prompting further investigation.
02
Asthma
Variable wheeze, breathlessness, night or exercise triggers and objective reversibility support asthma over isolated cough. when timing, examination and trajectory are integrated.
03
Bronchiectasis or cystic fibrosis
Clubbing, poor growth, recurrent infection, abnormal cultures or persistent wet cough directs CT and CF evaluation.
04
Foreign body or aspiration
Abrupt onset, focal signs or feeding association requires bronchoscopy or swallowing assessment despite normal routine imaging.
05
Post-infectious, tic or upper-airway cough
Gradual improvement, characteristic suppressibility or prominent rhinitis can support these after lower-airway red flags are excluded.
1Identify physiological instability and red flags and establish wet versus dry quality.
2Take onset, trigger, feeding, infection and exposure history and examine growth, clubbing and focal signs.
3Obtain chest radiography and spirometry when feasible, then select rather than scatter further tests.
02WetTreat PBB only when phenotype fitsIsolated daily wet cough persists without another specific pointer.+
1Send airway culture where feasible and give an appropriate 2-week co-amoxiclav course using current BNF-C dosing.
2Review for complete resolution and confirm adherence and dose.
3Investigate bronchiectasis and causes if cough persists after 2–4 weeks or recurs repeatedly.
Complications
01
Missed progressive lung disease
Labelling wet cough as benign delays diagnosis of bronchiectasis, CF, aspiration or retained foreign body. when recognition or effective treatment is delayed.
02
Structural airway injury
Ongoing infection and aspiration can produce irreversible bronchial dilatation, fibrosis and impaired lung growth. when recognition or effective treatment is delayed.
03
Medicine-related harm
Repeated antibiotics, corticosteroids and acid suppression cause adverse effects and diagnostic anchoring without a compatible phenotype.
04
Functional and family impact
Persistent cough disrupts sleep, school, exercise and relationships and can reinforce anxiety or tic behaviour. when recognition or effective treatment is delayed.
Monitoring and follow-up
Define the expected endpoint and review date for every treatment trial.
Document whether wet cough resolves completely, partially or recurs after antibiotic.
Track growth, activity, sleep, school and oxygenation alongside cough frequency.
Reassess new fever, haemoptysis, weight loss, focal signs or breathlessness urgently.
Review inhaler technique and objective asthma evidence before stepping up ICS.
Reduce smoke and vape exposure with household support, not blame.
Refer recurrent or unexplained cough rather than cycling through empirical medicines.
Special situations
Children swallow sputum
A caregiver's wet-cough description is clinically meaningful even when no sputum sample is produced.
Four weeks prompts thought
Investigation should begin earlier when red flags exist and should not be postponed simply to reach an 8-week label.
PBB requires complete response
Partial improvement is not diagnostic and should reopen adherence, organism, bronchiectasis and aspiration assessment.
Normal radiography has limits
Radiolucent foreign body and early bronchiectasis can remain invisible despite clinically important disease.
A therapeutic trial is an experiment
State the hypothesis, duration and measurable response and stop treatment when the predicted result does not occur.
Common pitfalls
01
Do not call a daily wet cough normal.
02
Do not wait 8 weeks when a foreign body or serious red flag is present.
03
Do not exclude foreign body or bronchiectasis from a normal radiograph.
04
Do not diagnose asthma from isolated cough without compatible variability.
05
Do not repeat antibiotics indefinitely for recurrent wet cough.
06
Do not prescribe acid suppression without reflux-related features.
07
Do not label cough psychogenic before positive assessment and red-flag exclusion.
08
Do not end follow-up without a defined recovery or escalation point.
Asthma causes variable wheeze, breathlessness, triggers and objective airflow or inflammatory evidence. Isolated dry cough without these features should not receive escalating inhaled corticosteroid indefinitely.
Post-infectious cough gradually improves after viral illness or pertussis. Antibiotics do not shorten a recovering viral cough; pertussis treatment mainly reduces transmission within its window.
Somatic or tic cough is diagnosed positively after organic red flags are excluded; characteristic distractibility, suppressibility or absent sleep cough can support it. Avoid dismissive language.
Do not empirically treat gastro-oesophageal reflux without compatible regurgitation, pain, dysphagia or aspiration features; acid suppression can cause harm.
Remove smoke and vape exposure, check vaccination and provide a defined follow-up endpoint. Worsening breathing, haemoptysis, fever, weight loss or reduced intake needs earlier review.
Neonatal onset, feeding difficulty, cough with meals or recurrent aspiration suggests congenital, ciliary or swallowing disease.
TB contact, travel, weight loss, fever or night sweats requires prompt specialist and public-health investigation.
Progressive breathlessness, exercise limitation, cardiac signs, immune deficiency or abnormal spirometry prevents a nonspecific-cough label.
Directed bronchoscopy, CF, ciliary, immune or swallow tests
Why
Investigate specific red flags and treatable causes.
Interpretation and limitations
Sudden focal disease prioritises bronchoscopy; multisystem and feeding phenotypes determine other specialist tests.
03DrySeek objective variable diseasePersistent cough is dry without suppurative red flags.+