Croup

Croup (laryngotracheobronchitis) is a common viral infection causing inflammation and edema of the subglottic larynx, trachea, and bronchi — the narrowest, non-distensible part of a young child's airway — producing the classic triad of a seal-like barking cough, hoarseness, and inspiratory stridor.^[1] It occurs most often between 6 months and 3 years of age, though it can present as early as 3 months and as late as 15 years, and is caused by respiratory viruses, most commonly parainfluenza virus types 1 and 3; influenza A and B, adenovirus, respiratory syncytial virus, human metapneumovirus, coronaviruses (including COVID-19), and mycoplasma have also been implicated. Most croup is mild and self-limited, resolving within about 48 hours (occasionally up to 6 days), and the large majority of affected children are managed successfully as outpatients. A single dose of oral dexamethasone is the standard of care for essentially every child diagnosed with croup, regardless of severity — this is the single most important pharmacologic decision in croup management and should not be reserved only for moderate-to-severe presentations.^[2]

Typical presentation

Croup usually begins with 1-2 days of nonspecific upper-respiratory symptoms — rhinorrhea, mild cough, and low-grade fever — before the characteristic seal-like barking cough, hoarseness, and inspiratory stridor emerge. Fever can reach up to 40°C but is not required for the diagnosis.

Symptoms are classically worse at night, improve during the day, and are markedly aggravated by agitation and crying — a child who looks comfortable while calm in a caregiver's lap can still have significant stridor and retractions once upset, so severity assessment should account for this variability rather than relying on a single calm snapshot.

Obstructive symptoms generally resolve within 48 hours of onset; a minority of children remain symptomatic for up to 6 days.

Physical examination findings

• Stridor — typically inspiratory; biphasic or expiratory stridor suggests more severe airway narrowing.
• Chest wall retractions (suprasternal, intercostal, subcostal) and visible respiratory distress, present to varying degrees depending on severity.
• Voice/cry — hoarse, but the child can usually still cry and speak, unlike the muffled "hot potato" voice or near-inability to speak seen with epiglottitis.
• Signs of impending respiratory failure develop over several hours and include reduced respiratory effort, pallor, cyanosis, a dusky appearance, decreased breath sounds, and lethargy or a decreased level of consciousness — these are late findings that must never be missed (see Red Flags and Refer).

• Age 6 months to 3 years (the period of greatest susceptibility); croup can occur as young as 3 months or as old as 15 years, and is rare beyond that.
• Male sex.
• Recent or concurrent viral upper respiratory infection — parainfluenza virus types 1 and 3 are the most common cause; influenza A/B, adenovirus, RSV, human metapneumovirus, coronaviruses (including COVID-19), and mycoplasma are also implicated.
• Fall and early-winter seasonality, reflecting the circulation pattern of parainfluenza virus.
• A personal history of prior croup episodes or an underlying airway abnormality (e.g., subglottic stenosis, laryngomalacia) increases the risk of recurrent or atypical (spasmodic) croup and should prompt evaluation.

Differentiating croup from its dangerous mimics

Several conditions can present with acute stridor and must be actively distinguished from croup, since some require completely different, urgent management.^[3]

Rarer causes of acute stridor include severe allergic reaction/angioedema (rapid onset, possible urticaria/hypotension, personal or family history of allergy), peritonsillar/retropharyngeal or other upper-airway abscess (drooling, neck stiffness, unilateral swelling, more gradual onset), and diphtheria (extremely rare, seen only with inadequate immunization; membranous pharyngitis is characteristic).

History

• Onset and duration of barking cough, hoarseness, and stridor; ask specifically whether stridor is present at rest or only with agitation/crying.
• Preceding upper respiratory symptoms (rhinorrhea, low fever) over the prior 1-2 days.
• Oral intake tolerance and hydration status.
• Any history of prior croup episodes, a known airway abnormality, or recent choking/foreign-body exposure.
• Immunization status (Haemophilus influenzae type b, diphtheria) — relevant to the differential diagnosis, not to croup management itself.

Physical examination

• Assess the child while calm, ideally on a caregiver's lap — unnecessary handling, throat examination, or IV attempts can provoke crying and transiently worsen airway obstruction and the apparent severity.
• Vital signs, with particular attention to respiratory rate and work of breathing.
• Presence and timing of stridor (at rest vs. only with agitation), chest wall retractions, and air entry on auscultation.
• Level of consciousness and colour — lethargy, pallor, or cyanosis indicate impending respiratory failure.

Investigations

Croup is a clinical diagnosis; no laboratory testing or imaging is routinely required.

• Lateral and anteroposterior soft-tissue neck radiographs are reserved for atypical presentations or a child not responding to treatment as expected — they are not needed to confirm a typical presentation. A classic but non-mandatory finding is subglottic narrowing on the AP view (the "steeple sign").
• Pulse oximetry is reserved for more severe croup, since marked airway obstruction can eventually cause hypoxia and hypercapnia; it is not needed for mild, typical cases.
• Routine bloodwork and viral testing are not needed to manage typical croup and do not change treatment.

Severity assessment: the Westley Croup Score

The Westley Croup Score combines 5 items — level of consciousness, cyanosis, stridor, air entry, and retractions — into a single severity score from 0 to 17.^[6] Unlike a simple point-per-criterion tool, each criterion carries a different maximum weight (cyanosis at rest alone contributes 5 points, while stridor at its worst contributes only 2), so this chapter provides the full scoring table for teaching and structured severity communication rather than a live calculator — this non-uniform point weighting does not meet the simple, unambiguous point-sum bar required before an interactive scoring tool is safe to offer.^[3]

Total score interpretation: 0-2 mild, 3-5 moderate, 6-11 severe, ≥12 impending respiratory failure.

• Relieve upper-airway obstruction and reduce the work of breathing.
• Shorten the duration and severity of stridor, cough, and retractions.
• Avoid unnecessary intubation and hospitalization.
• Minimize anxiety and agitation in the child — agitation worsens turbulent airflow through the narrowed airway and can itself precipitate progression — and reduce caregiver distress.
• Correctly identify and manage red-flag mimics (epiglottitis, bacterial tracheitis, foreign body aspiration) rather than treating one of them as routine croup.
• Prevent avoidable return visits by ensuring effective initial dosing and clear caregiver counselling on red-flag recognition.

• Keep the child calm, ideally held upright on a caregiver's lap in a calm, reassuring environment — agitation and crying increase turbulent airflow through the narrowed airway and can transiently worsen stridor and distress; minimize unnecessary examinations, needle sticks, or separation from the caregiver.
• A brief period of exposure to cool or cold outdoor air (dressed warmly, never left unattended) is a reasonable, low-risk adjunct — a randomized trial found a higher proportion of children improved after cold outdoor air exposure than after room-temperature exposure.^[10]
• Humidified air, bedside mist, and mist tents have not been shown to reduce respiratory distress in croup and should not be relied on as therapy — a wet, cold, enclosed mist tent that separates a child from their caregiver can itself provoke anxiety and agitation, which is counterproductive.^[11]
• Oxygen, when needed for hypoxia or significant respiratory distress, is given alongside dexamethasone and epinephrine, never as a substitute for them; "blow-by" oxygen (a hose held near the child's face) is often best tolerated, and oxygen should never be forced on an agitated child.
• Helium-oxygen (heliox) mixtures may be considered as an adjunct in severe croup at centres equipped to deliver and monitor it, but current evidence is too limited to support routine or general use.^[12]
• Ensure adequate oral fluid intake for hydration and comfort; offer antipyretic/analgesic dosing (see Pharmacologic Treatment Options) for fever or throat discomfort.

Pregnancy and breastfeeding

Not applicable — croup is a pediatric condition and does not occur in pregnant or breastfeeding adults; no pregnancy/lactation-specific dosing considerations apply to this chapter.

Infants under 3 months

Croup is uncommon in this age group. Stridor in a young infant should prompt evaluation for an underlying structural airway abnormality (e.g., laryngomalacia, subglottic stenosis, vascular ring) rather than being assumed to be viral croup — refer for further assessment.

Recurrent (spasmodic) croup or croup outside the typical age range

Three or more episodes, or croup presenting outside the typical 6-month-to-3-year window (especially in older children or with onset before 3 months), should prompt referral for otolaryngology evaluation to rule out an underlying structural airway lesion such as subglottic stenosis or a subglottic hemangioma.

Underlying chronic airway, cardiac, or immunocompromising conditions

Children with Down syndrome, other conditions predisposing to baseline airway narrowing, chronic lung or cardiac disease, or immunocompromise have a lower threshold for hospitalization and closer monitoring, since croup can progress more quickly or severely in these children.

Concurrent varicella (chickenpox)

A single dose of corticosteroid for croup does not need to be withheld from a child with active or recent varicella infection — recent corticosteroid use has not been shown to increase the risk of complicated varicella in otherwise immunocompetent children in case-control data.^[13]

Renal / hepatic impairment

No dose adjustment is required for a single dose of dexamethasone. Use caution with repeated dosing in significant hepatic impairment; renal impairment does not require dose adjustment for the corticosteroids or nebulized epinephrine used in croup.

Reassess a child who receives nebulized epinephrine at around 20-30 minutes (near peak effect) and again before discharge, at a minimum of 2-3 hours after the dose, to confirm stridor is not present at rest and the child is tolerating oral fluids. A child who received oral dexamethasone alone for mild croup can generally be discharged after a shorter period of observation once comfortable, particularly if this is not the first assessment for the episode.

Give caregivers a clear expected course (symptoms often peak over the first 2-3 nights before improving, with full resolution typically by about a week) and explicit red-flag return instructions rather than only a vague "come back if it gets worse."

No routine follow-up visit or repeat testing is needed after an uncomplicated, resolved episode. Refer for otolaryngology assessment if the child has 3 or more discrete croup episodes or croup outside the typical age range.

1. Reassess the diagnosis before repeating treatment — a child not responding as expected to dexamethasone and nebulized epinephrine may have epiglottitis, bacterial tracheitis, a foreign body, or another cause of stridor rather than treatment-resistant croup.
2. If stridor at rest persists or worsens despite dexamethasone and an initial dose of nebulized epinephrine, repeat nebulized epinephrine with continuous monitoring and reassess.
3. If the child is near respiratory failure or requires back-to-back epinephrine dosing, escalate immediately to a monitored setting with continuous cardiac monitoring, and involve pediatric critical care/anesthesia for advanced airway planning.
4. If vomiting or distress prevents oral dexamethasone and parenteral dosing is not tolerated or available, use nebulized budesonide instead.
5. If symptoms recur several hours after apparent improvement — well beyond epinephrine's roughly 1-2 hour window of effect — treat this as ongoing or worsening croup rather than assuming a rebound effect, and continue observation and re-treatment as clinically indicated.
6. Refer for otolaryngology assessment if croup is recurrent (3 or more episodes) or persists well beyond the typical course (more than about a week).

• Withholding dexamethasone from a child with mild croup on the assumption that corticosteroids are only for moderate-severe disease — current evidence supports benefit across the full severity spectrum.
• Relying on humidified air, cool mist, or a mist tent as primary therapy — not supported by current evidence, and a mist tent can increase a child's distress by separating them from their caregiver in a cold, wet, enclosed space.
• Discharging a child immediately after nebulized epinephrine without an adequate observation period.
• Using inhaled beta2-agonists (e.g., salbutamol) for croup — the upper airway has no smooth muscle for these drugs to act on.
• Giving over-the-counter cough and cold products (antitussives, decongestants) to a child under 6 years of age.
• Attempting an oropharyngeal examination, IV access, or laying a child supine when epiglottitis is suspected — this can precipitate complete airway obstruction.
• Assessing severity only while the child is calm — stridor and retractions are most apparent during agitation or crying, and a snapshot taken only at rest can underestimate true severity.
• Missing a cue (recurrent episodes, atypical age, poor response to therapy) to investigate for an underlying structural airway lesion.
• Routinely combining nebulized budesonide with oral dexamethasone — no added clinical benefit has been shown, only added cost and treatment burden.
• Using antibiotics for typical viral croup.

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Corticosteroids

Mainstay of croup therapy for every severity level — the single most important pharmacologic decision in croup management.

Adrenergic agonists

For moderate-to-severe croup with stridor at rest or significant distress — always given alongside, not instead of, dexamethasone.

Analgesics / antipyretics

Comfort measures only — neither treats the underlying airway obstruction.

Not effective / not recommended

These agents are specifically not part of croup management and should not be used:

• Inhaled beta2-agonists (e.g., salbutamol) — the upper airway contains no smooth muscle for these drugs to act on; no trial evidence supports benefit.
• Antitussives and decongestants — no rational basis for benefit, and specifically discouraged by Health Canada in children under 6 years of age.
• Routine antibiotics — croup is viral. Reserve broad-spectrum IV antibiotics, chosen and dosed under specialist/ICU direction, for confirmed or strongly suspected bacterial tracheitis or epiglottitis, which are managed as airway emergencies outside the scope of this table.
• Helium-oxygen (heliox) — may be considered as an adjunct in severe croup at centres able to deliver and monitor it, but current evidence is too limited to support routine use.