A diagnosis of croup is made clinically on the basis of a compatible history and examination findings. Investigations are rarely helpful.

Suspect croup in a child with a sudden onset of a seal-like barking cough. Hoarse voice is also common.

Symptoms are typically worse at night and increase with agitation.

Prodromal, non-specific upper respiratory tract symptoms (coryza, non-barking cough, mild fever) may have been present for between 12 and 72 hours.

Progressive upper airway obstruction can result in the development of stridor and respiratory distress.

Take care not to frighten the child as agitation can worsen symptoms.

Ensure the child is seated comfortably in the parent/carer's lap, to ensure comfort.

Do not reposition the child from the posture they have naturally adopted as this will be one that minimises airway obstruction.

Categorize the severity of the symptoms and signs to guide management options:

Mild — seal-like barking cough but no stridor or sternal/intercostal recession at rest.

Moderate — seal-like barking cough with stridor and sternal recession at rest; no (or little) agitation or lethargy.

Severe — seal-like barking cough with stridor and sternal/intercostal recession associated with agitation or lethargy.

Impending respiratory failure — minimal barking cough, stridor may become harder to hear. Increasing upper airway obstruction, sternal/intercostal recession, asynchronous chest wall and abdominal movement, fatigue, pallor or cyanosis, decreased level of consciousness or tachycardia. The degree of chest wall recession may diminish with the onset of respiratory failure as the child tires. A respiratory rate of over 70 breaths/minute is also indicative of severe respiratory distress.

Bacterial tracheitis — may present with fever, sudden onset stridor, and respiratory distress, following a viral-like respiratory illness from which the person appears to be recovering but then becomes acutely worse.

Epiglottitis — may present with sudden onset high fever, dysphagia, drooling, anxiety, non-barking cough, and their preferred posture is sitting upright with head extended. Note: This is rarely seen since widespread immunisation against Haemophilus influenzae B.

Foreign body in upper airway — may present with sudden onset dyspnoea and stridor, usually a clear history of foreign body inhalation or ingestion, no prodrome or symptoms of viral illness, and no fever (unless secondary infection).

Retropharyngeal/peritonsillar abscess — may present with dysphagia, drooling, stridor (occasionally), dyspnoea, tachypnoea, neck stiffness, and unilateral cervical adenopathy. Onset is typically more gradual than with croup and is often accompanied by fever.

Angioneurotic oedema — may present with acute swelling of the upper airway that may cause dyspnoea and stridor. Fever is uncommon. Swelling of face, tongue, or pharynx may be present. Can occur at any age.

Allergic reaction — may present with rapid onset of dysphagia, stridor, and possible cutaneous manifestations (urticarial rash). Can occur at any age. Suspicion should be further raised if there is a personal or family history of prior episodes, or allergy.