Croup
A usually viral upper-airway infection causing subglottic swelling and a barking cough, hoarse voice and inspiratory stridor; keep the child calm, give steroid treatment when indicated, and treat stridor at rest or deterioration as an airway emergency.
Definition
Croup is an acute, usually viral infection of the larynx and subglottic airway in a young child, producing a barking cough, hoarseness and inspiratory stridor.
Epidemiology
Croup is commonest in young children, particularly around 6 months to 3 years, and symptoms often worsen overnight. Most episodes are mild and self-limiting, but significant upper-airway obstruction can develop.
Pathophysiology
Viral inflammation produces oedema in the larynx and subglottic airway. The narrowed airway generates turbulent inspiratory flow, causing stridor, while laryngeal and tracheal inflammation produces hoarseness and the barking cough. Crying increases airflow demand and worsens the obstruction.
First principles
The sound identifies the level of obstruction
Croup inflames the larynx and subglottic airway. Turbulent airflow through the narrowed upper airway produces a barking cough, hoarseness and inspiratory stridor; stridor at rest and increasing recession indicate more significant obstruction than a barking cough alone.1,2,3
Distress worsens the obstruction
Crying, agitation and unnecessary examination increase airflow demand and can worsen upper-airway narrowing. Assess the child quietly on a carer's lap, keep them upright and avoid procedures that are not needed for immediate treatment.1,3,4
Steroid reduces the swelling; adrenaline buys time
A corticosteroid reduces inflammatory airway oedema over hours. Nebulised adrenaline causes rapid but temporary improvement in significant stridor or distress and should be used as a bridge while the child is observed and senior airway support is available, not as a substitute for assessment.1,5,6
Drooling and toxicity are diagnostic warnings
A toxic or very unwell child with high fever, drooling, dysphagia, muffled voice or a preferred sitting position may have epiglottitis, bacterial tracheitis or another dangerous upper-airway process rather than simple croup. Do not force a throat examination; minimise distress and obtain urgent senior anaesthetic and ENT support.4,2,3
Disposition is based on response and safety
Most mild croup can be managed at home with calm care, fluids and clear safety-netting. Persistent stridor at rest, significant recession, repeated adrenaline, poor intake, atypical features, very young age or an unsafe return plan lowers the threshold for paediatric assessment or admission.1,2,5
Presentation
A young child, often after a coryzal illness, with a sudden or nocturnally worse barking cough, hoarse voice and inspiratory stridor. Assess stridor at rest, recession, agitation or lethargy, colour, hydration and the ability to speak or feed without distress.1,2,3
Cardinal features
- Barking or seal-like cough
- Hoarse voice or cry
- Inspiratory stridor
- Coryzal prodrome and low-grade fever
- Symptoms worse at night or with crying
- Variable work of breathing, from none to marked recession
Red flags
- Stridor at rest with significant recession or rapidly worsening breathing
- Cyanosis, pallor, exhaustion, reduced consciousness or a child who is difficult to wake
- Drooling, dysphagia, muffled voice or a toxic-looking child
- Child too breathless to speak, drink or be comforted
- Agitation with worsening obstruction, or a quiet, lethargic child suggesting fatigue
- Sudden onset after choking, facial swelling or urticaria suggesting foreign body or anaphylaxis
- Failure to improve after steroid or recurrence after nebulised adrenaline
Investigations
Undisturbed clinical assessment
Croup is diagnosed clinically. Assess the barking cough, voice, stridor at rest or only when upset, work of breathing, recession, respiratory rate, colour, alertness, hydration and ability to speak or feed. Keep the child with the carer and avoid unnecessary distress.
Expected finding: Barking cough, hoarseness and inspiratory stridor with severity determined by stridor at rest, recession and behaviour; a normal oxygen saturation does not exclude clinically important upper-airway obstruction.
1,2,3Pulse oximetry when it will not distress the child
Oximetry can identify hypoxia in significant obstruction, but a normal value does not rule out dangerous upper-airway narrowing and applying a probe must not delay treatment or agitate the child. Give oxygen if hypoxic while escalating the airway assessment.
Expected finding: Often normal in mild or moderate croup; hypoxia is a late and worrying sign suggesting severe obstruction or another diagnosis.
1,4No routine imaging or laboratory testing
Typical croup does not need a throat swab, blood tests or neck radiograph. Avoid throat examination if epiglottitis is possible. Consider targeted investigations only after senior assessment when the diagnosis is atypical, a foreign body or bacterial infection is suspected, or an airway procedure is being planned.
Expected finding: No routine investigation is expected in straightforward croup; focal or toxic features redirect the pathway.
1,4Response and observation after treatment
Repeated clinical observations are more useful than a single score. Reassess stridor at rest, recession, behaviour, hydration, oxygenation and the duration of response after steroid or nebulised adrenaline; local paediatric protocols determine the observation period and disposition.
Expected finding: Improvement in stridor and work of breathing supports croup responding to treatment; persistent or recurrent symptoms require senior review and possible admission.
5,3,1Management
| Step | Detail | Source |
|---|---|---|
| Keep the child calm and protect the airway | Keep the child upright and with their carer, minimise handling and avoid forcing them to lie down or open their mouth. Give oxygen only if hypoxic and in a way that causes the least distress. Call for senior paediatric, anaesthetic and ENT help early if the child is tiring, cyanosed, severely distressed or has a concerning alternative diagnosis.1,4,2 | NICE CKS Croup; RCPCH upper-airway-obstruction guidance |
| Give a single corticosteroid dose according to the paediatric protocol | For clinically significant croup, give a single oral dose of dexamethasone; a commonly used UK regimen is 0.15 mg/kg, with the exact dose, maximum and route checked in the current BNF/BNFc and local paediatric guideline. If oral treatment is not possible, use the local alternative such as nebulised budesonide or parenteral dexamethasone. Do not keep repeating steroids without senior review.1,5,7,6 | NICE CKS Croup; current NHS paediatric croup protocols; BNF/BNFc |
| Use nebulised adrenaline for significant or worsening obstruction | For stridor at rest with significant distress, deterioration or severe croup, give nebulised adrenaline under the local paediatric emergency protocol while arranging senior review. A current NHS Highland protocol uses 1:1000 adrenaline at 400 micrograms/kg up to 5 mg; verify the preparation and dose in the local protocol. Improvement is temporary, so observe for recurrence and do not discharge solely because the first nebulisation helped.5,3 | NHS Highland paediatric croup guideline, updated 2025 |
| Escalate severe, atypical or non-responding disease | Arrange urgent hospital care for severe breathing difficulty, persistent stridor at rest, cyanosis, exhaustion, reduced consciousness, inability to swallow or poor response to treatment. Involve paediatric critical care, anaesthetics and ENT for impending respiratory failure; prepare for controlled airway management rather than repeatedly distressing the child.4,2,3 | RCPCH upper-airway-obstruction guidance; NHS croup information |
| Avoid harmful or ineffective measures | Do not use steam or a steamy room because it does not treat the obstruction and can cause scalds. Do not use cough medicines that may sedate the child or mask deterioration. Do not force throat examination, and do not treat presumed epiglottitis or bacterial tracheitis as uncomplicated croup.2,3,4 | NHS croup information; RCPCH upper-airway-obstruction guidance |
| Discharge mild, improving disease with safety-netting | Only manage at home when the child is clinically stable, breathing comfortably without stridor at rest, drinking adequately and the diagnosis is secure. Advise calm upright care, fluids, age-appropriate analgesia for discomfort or fever, regular checks including overnight and no smoking around the child. Give clear instructions to call 999 for struggling or noisy breathing, cyanosis, unusual drowsiness, drooling or difficulty swallowing, inability to drink, or rapid deterioration; arrange reassessment if symptoms recur or fail to improve.2,3 | NHS croup information; Cambridge University Hospitals croup and stridor guidance |
Illustrations
Differentials
Epiglottitis
Rapidly unwell child with high fever, drooling, dysphagia, muffled voice or a preferred upright position, often without the classic barking cough.
Bacterial tracheitis
Toxic appearance, high fever and thick secretions or deterioration despite initial croup treatment.
Inhaled foreign body
Sudden onset after choking with focal or persistent unilateral signs.
Anaphylaxis or angioedema
Rapid onset after exposure with facial or tongue swelling, urticaria, wheeze or circulatory compromise.
Retropharyngeal or peritonsillar infection
Fever, toxic appearance, drooling, neck stiffness, muffled voice or focal throat findings.
Complications
- Progressive upper-airway obstruction and respiratory failure
- Hypoxia
- Dehydration from poor intake
- Bacterial tracheitis or another missed alternative diagnosis
- Recurrent or atypical croup requiring airway assessment
Prognosis
Most children improve over 1 to 2 days with supportive care and, when indicated, a single corticosteroid dose. Severe or atypical croup may require nebulised adrenaline, admission and airway support; recurrent or atypical episodes warrant assessment for another cause.
Guidelines
- Croup (NICE CKS)
- Acute upper airway obstruction in children (RCPCH)
References
- NICE CKS: Croup (Clinical Knowledge Summary, accessed for current diagnosis and management pathway)
- NHS: Croup (NHS condition information, reviewed 23 September 2025)
- Cambridge University Hospitals: Children's croup and stridor (Paediatric emergency information, approved 9 December 2025)
- RCPCH: Acute upper airway obstruction in children (Paediatric emergency guidance)
- NHS Highland: Croup paediatric guideline (Local paediatric therapeutic guideline, updated August 2025)
- BNF: Dexamethasone (BNF medicine monograph)
- Sheffield Children's NHS Foundation Trust: Acute stridor and croup (Emergency medical guideline, 2025)
Evidence checked: 2026-08-03
This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.