Croup

Overview

Croup, also known as largnotracheobronchitis, is a usually self limiting upper airway viral infection causing upper airway obstruction. Croup is more common in boys than in girls, usually occurs between six and 36 months of age, and peaks during the second year of life. Croup is usually caused by viruses, which are detected in up to 80 percent of patients (parainfluenza the most common).

Croup is the clinical syndrome of:

• Hoarse voice
• Barking cough
• Inspiratory Stridor
• Respiratory distress

Aetiology & Risk Factors

Aetiology

Croup is usually caused by a respiratory virus, most commonly:

• Parainfluenza virus types 1 and 3
• Influenza A or B
• Respiratory syncytial virus
• Adenovirus
• Human metapneumovirus
• SARS-CoV-2

Antibiotics are not effective in uncomplicated croup because it is viral.

Risk factors

• Age between 6 months and 3 years
• Male sex
• Autumn and winter respiratory-virus seasons
• Previous episodes of croup
• Family history of croup
• Smaller or structurally abnormal upper airway
• Atopy or family history of asthma in recurrent spasmodic croup

Presentation below 6 months, recurrent episodes or unusually prolonged or severe disease should prompt consideration of an underlying airway abnormality.

Pathophysiology

• Viral infection causes inflammation and oedema of the larynx, trachea and sometimes bronchi.
• The subglottic airway becomes narrowed.
• Children are particularly affected because their airway diameter is small; minor mucosal swelling can produce a major increase in airflow resistance.
• Turbulent airflow through the narrowed upper airway produces inspiratory stridor.
• Vocal-cord and laryngeal inflammation produces hoarseness and the characteristic barking cough.
• Crying, agitation and distress increase airflow turbulence and can significantly worsen obstruction.
• Severe narrowing may cause respiratory muscle fatigue, hypoxaemia and complete airway obstruction.

Clinical Manifestation

Typically, viral croup develops over days with a upper respiratory tract infection, with low-grade fever and coryza followed by a barking cough and various degrees of respiratory distress. In most children, the symptoms subside quickly with resolution of the cough within two days.

• Agitation
• Inspiratory stridor
• Barking Cough
• Hoarse voice
• Tracheal Tug
• Lethargy
• Abrupt onset of symptoms
• Symptoms worse at night

Diagnosis

Differentials for stridor

• Croup (common)
• Bacterial tracheitis (uncommon)
• Foreign body
• Epiglottitis (rare)
• Spasmodic croup
• Retropharyngeal abscess
• Laryngomalacia

Feature	Croup	Bacterial tracheitis	Epiglottitis	Foreign body
Typical age	6 months–4 years	5–10 years	2–8 years	Any child
Onset	Gradual over 1–2 days	Rapid, usually <24 hours	Rapid, usually <24 hours	Sudden, usually <24 hours
History	Coryza and barking cough	Fatigue, cough and sore throat	Severe sore throat and dysphagia	Possible choking episode
Temperature	Low-grade fever	High fever	High fever	Usually afebrile
Clinical signs	Harsh stridor, hoarseness and non-toxic appearance	Mucopurulent secretions, softer stridor and toxic appearance	Tripod position, drooling, softer stridor and toxic appearance	Abrupt respiratory symptoms; usually non-toxic appearance
Intubation/antibiotics	Usually not required	Often required	Often required	Airway intervention or foreign-body removal may be required

Three factors to consider when deciding whether the presence of stridor and respiratory accessory muscle use relate to croup or another disease.

1. Age of child

• <3 month more likely to be structural airway problem (ie. Laryngomalacia  or Tracheomalacia)
• ~6months consider subglottic haemangioma
• 1-3 years with acute onset without fever may have inhaled a foriegn body usually with expiratory wheeze (rather then inspiratory stridor)

2. Character is stridor

• Inspiratory and expiratory stridor increases the likelihood to an underlying fixed tracheal obstruction (i.e subglottic stenosis)

3. Toxicity of child

• Children with croup do not appear toxic
• Toxic child consider meningitis or epiglottitis

Investigations

Croup is a clinical diagnosis based on early respiratory infections followed by a barking cough

• Chest X-ray
• Neck X-ray – steeple sign

Classification

Mild Airway Obstruction

• Barking cough without inspiratory stridor

Moderate Airway Obstruction

• Stridor at rest
• Tracheal tug
• Chest wall recession

Severe Airway Obstruction

• Persisting stridor
• Tracheal tug
• Chest wall recession
• Aaethetic/restless

Soft stridor, irritability, tachycardia, pallor indicates imminent airway obstruction

Treatment

A single dose of dexamethasone is recommended in all patients with croup, including those with mild disease. Nebulized epinephrine is an accepted treatment in patients with moderate to severe croup.

Mild Airway Obstruction

• No need for specific treatment

Moderate Airway Obstruction

• Corticosteroids
  • Oral Prednisalone (1mg/kg)
  • Dexamethasone (0.3mg/kg)
• +/- Nebulised Adrenaline – Budesonide (2mg)

Severe Airway Obstruction

• Oxygen
• Corticosteroids
  • Oral Prednisalone (1mg/kg)
  • Dexamethasone (0.3mg/kg)
• +/- Nebulised Adrenaline – Budesonide (2mg)
• Monitor

Complications & Prognosis

Complication 

Croup is a benign condition with a low mortality rate

Prognosis

• Most cases are mild and resolve within 3–7 days.
• The barking cough often improves within approximately 48 hours but may persist longer.
• Fewer than 1% of cases become severe.
• Hospital admission is uncommon, and endotracheal intubation is rarely required.
• Croup usually causes no permanent airway or lung damage.
• Prognosis is poorer with very young age, pre-existing airway narrowing, neuromuscular disease or severe respiratory compromise.

Croup vs. Spasmodic Croup

Typically, viral croup develops over days with a upper respiratory tract infection, with low-grade fever and coryza followed by a barking cough and various degrees of respiratory distress. In most children, the symptoms subside quickly with resolution of the cough within two days.

Conversely, spasmodic croup is said to be more in atopic, older children. Spasmodic croup comes on rapidly overnight in children who were perfectly well when they went to sleep. Spasmodic croup often runs a shorter course.

CONDITION	HISTORY	EXAMINATION	WORK UP	AETIOLOGY
Laryngotracheitis (croup)	Barking cough, coryza	Low-grade fever, nasal flaring, respiratory retractions, stridor	Generally not indicated	Parainfluenza virus types 1 to 3, influenza, respiratory syncytial virus
Spasmodic croup (recurrent croup)	Usually recurrent, short duration, barking cough	Afebrile, less retractions and nasal flaring	Generally not indicated, but bronchoscopy (especially in children younger than three years) and endoscopy may be considered	Same as viral croup, with possible allergic component or gastroesophageal reflux

References

1. Royal Children’s Hospital Melbourne. Croup (laryngotracheobronchitis): clinical practice guideline [Internet]. Melbourne: Royal Children’s Hospital; updated 2024 Sep.
2. Agency for Clinical Innovation. Croup-like illness: Paediatric Emergency Care Assessment and Treatment protocol [Internet]. Sydney: NSW Health; 2026.
3. Ortiz-Alvarez O; Canadian Paediatric Society, Acute Care Committee. Acute management of croup in the emergency department. Paediatr Child Health. 2017;22(3):166–169. Updated 2026 Mar 6.
4. Aregbesola A, Tam CM, Kothari A, Le ML, Ragheb M, Klassen TP. Glucocorticoids for croup in children. Cochrane Database Syst Rev. 2023;1(1). doi:10.1002/14651858.CD001955.pub5.
5. Bjornson CL, Russell KF, Vandermeer B, Durec T, Klassen TP, Johnson DW. Nebulized epinephrine for croup in children. Cochrane Database Syst Rev. 2013;(10). doi:10.1002/14651858.CD006619.pub3.