Viral croup is the most common form of airway obstruction in children 6 months to 6 years of age. When symptoms are severe enough to seek medical attention, oral dexamethasone is the preferred therapy because of cost, ease of administration, and efficacy. Intravascular and intramuscular dexa- methasone are reasonable alternatives. Nebulized steroids are more expensive and less efficacious than oral dexamethasone for the treatment of croup. Croup is a viral illness caused most commonly by parainfluenza viruses (types 1, 2, and 3). Croup can also be caused by influenza A and B, adenovirus, respiratory syncytial virus, rhinovirus, and enteroviruses. Croup can affect the larynx, trachea, bronchi, and lungs, causing inflammation and swelling. The subglottic area is particularly affected, resulting in a narrowed airway. Classic symptoms of croup include a barking cough, hoarse voice, inspiratory stridor, and varying degrees of respiratory distress. Croup most commonly affects children between 6 months and 6 years of age, with a peak incidence at 2 years. The incidence in children younger than 6 years of age is approximately 6 per 100 annually. The illness predominates in the fall and winter.

When a child presents with stridor, other diagnoses such as foreign body aspiration, angioedema, epiglottitis, and bacterial tracheitis must be considered in the differential. Croup is diagnosed clinically based on its characteristic history. It begins with 12 to 72 hours of nasal congestion and low-grade fevers, followed by hoarseness and a barky cough. Patients may also have inspiratory stridor and respiratory distress. Symptoms of croup are worse at night, when in the supine position, and with agitation and crying. Symptoms peak between 24 and 48 hours, and usually resolve within 1 week.