Key clinical points

No stridor or sternal/intercostal recession at restStridor and sternal recession at rest

No agitation or lethargy
Stridor and sternal/intercostal recession

Agitation or lethargy

  • Single dose oral dexamethsone (0.15 mg/kg)
  • Admit if moderate/severe (i.e. admit if stridor)
  • Moderate/severe
    • Oxygen
    • Nebulised epinephrine


Croup, also known as laryngotracheobronchitis, is a common viral infection of the upper airways in children. Inflammation of the larynx causes the classic barking cough, stridor, and may be accompanied by a low fever.

Prior to this typical presentation, a prodromal period of non-specific upper respiratory tract symptoms (coryza, non-barking cough, mild fever) may occur for 12-48 hours. The barking cough and respiratory distress then typically last 1-2 days before recovery.

Croup affects children between the ages of 6 months and 3 years, and is more common in autumn. The parainfluenza virus is most commonly implicated in croup.


  • Incidence: 250.00 cases per 100,000 person-years
  • Peak incidence: 1-5 years
  • Sex ratio: more common in males 1.4:1
Condition Relative
Viral upper respiratory tract infections120.00
Acute epiglottitis0.01
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


Aetiology is most commonly viral, with some cases caused by bacteria.

  • Parainfluenza virus is the principal cause of acute laryngotracheobronchitis, accounting for 75% of infections.
  • Other causes include influenza A and B, measles, adenovirus, and respiratory syncytial virus (RSV).

  • The common bacterial causes are Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.

Croup is droplet spread and outbreaks can occur in childcare settings or school, most commonly in autumn. Croup is more common in males (1.4:1).


  • Following a coryzal prodrome, white blood cells infiltrate the larynx, trachea and large bronchi, causing inflammation.
  • This inflammation causes oedema which results in partial airway obstruction.
  • When significant, this airway obstruction dramatically increases the work of breathing and causes the characteristic turbulent airflow known as stridor.

Clinical features

Children with croup may present to general practice or the Emergency Department (ED).

Croup is suggested by a coryzal prodrome which then progresses over 12 to 48 hours to include:
  • Low fever
    • Usually less than 38ÂșC
  • Hoarseness
  • Barking cough
    • Worse at night
  • Stridor
    • Insidious and progressive

As airway obstruction progresses, features of respiratory distress may develop:
  • Tachypnoea
  • Cyanosis
  • Head bobbing
  • Nasal flaring
  • Subcostal and intercostal recession
  • Suprasternal and sternal recession
  • Diaphragmatic breathing
  • Use of accessory muscles.

National Institute for Health and Care Excellence (NICE) Clinical Knowledge Summaries (CKS) suggest the following distinction between mild, moderate, and severe croup:
  • 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 agitation or lethargy.
  • Severe
    • Seal-like barking cough with stridor and sternal/intercostal recession associated with agitation or lethargy.


  • Croup is a primarily clinical diagnosis, suggested by the presence of barking cough and stridor, especially in the context of a local community outbreak.

  • For the vast majority of children presenting to primary/secondary care with symptoms of classic croup on history and physical examination, no further investigation is necessary.

  • In some cases, however, laboratory studies or radiographs may be useful to rule out differential diagnoses.

  • Indications for radiographic evaluation include:
    • Uncertainty about the diagnosis
    • Atypical course of illness
    • Inhaled foreign body is suspected
    • Recurrent croup
    • Inadequate response to appropriate therapeutic interventions

Differential diagnosis

The following diagnoses have similarities to croup, but can usually be differentiated through history and physical examination.

Viral upper respiratory tract infection (URTI)
  • Similarities
    • Common in young children
    • Causes coryza, cough and respiratory distress
  • Differences
    • Seal-like barking cough less common

  • Similarities
    • Causes cough, fever, and respiratory distress
  • Differences
    • Affects children < 2 years old
    • Causes wheeze
    • No barking quality to cough

  • Similarities
  • Differences
    • Usually seen in children 3-5 years of age
    • Absence of barking cough
    • Muffled hot potato voice
    • Tripod or sniffing position
    • An incomplete vaccination history more likely to be present

Foreign body aspiration
  • Similarities
    • Often < 3 years of age
    • Stridor
    • Dysphonia depending on location of foreign body
  • Differences
    • History suggestive of possible foreign body
    • Abrupt onset during daytime (croup usually night-time)
    • Minimal response to adrenaline nebuliser

Bacterial tracheitis
  • Similarities
    • Stridor
  • Differences
    • Usually school-age
    • Soft stridor 2-7 days after onset of URTI symptoms
    • Significant tracheal tenderness on palpation
    • Reluctant to cough because of pain

Other differential diagnoses include anaphylaxis and retropharyngeal abscess.

If the child is <6 months, consider laryngomalacia, tracheomalacia, or a vascular ring.


Croup may be managed in primary or secondary care, depending on the severity of symptoms. All children with moderate or severe croup should be referred to the emergency department (ED).

The principles of treatment in mild and moderate croup are symptomatic relief, while the prevention of further airway compromise is paramount in severe croup.

NICE CKS guidelines, last updated in 2019, suggest the following algorithm for the management of croup:

Primary care (mild illness)
  • Supportive care
  • Oral dexamethasone
  • Parents should be advised regarding:
    • The expected course of croup, including that symptoms usually resolve within 48 hours.
    • The need to take the child to hospital if stridor can be heard continually, the skin between the ribs is pulling in with every breath, and/or the child is restless or agitated.
    • The use of antipyretics in children distressed due to fever.
    • The need to check on the child regularly, including through the night.
  • Arrange follow-up, using clinical judgment to determine the appropriate interval.

Secondary care (moderate - severe illness)
  • All children with moderate-severe illness should be admitted
  • Supportive care
  • Oral dexamethasone
  • Nebulised epinephrine
  • Supplemental oxygen
  • The above advice should also be given

Children that present to the ED may be safely discharged home after 2 to 4 hours of observation following epinephrine administration, given they have no stridor at rest.


Complications of croup are generally due to airway obstruction caused by the oedema.

Respiratory distress is a significant complication of croup, manifesting as the signs listed above. This may progress to respiratory failure in some cases and even death.

Further complications are less common and include:
  • Pneumonia
  • Pulmonary oedema
  • Epiglottitis
  • Bacterial tracheitis