Croup is the most common cause of upper airway obstruction in children. It is characterized by acute onset of barky cough +/- stridor. The typical age of presentation is between 6 months and 5 years with a peak around 2 years. Consider other causes of upper airway obstruction such as bacterial tracheitis, epiglottitis and retropharyngeal abscess in children presenting with severe symptoms and a transient or lack of response to croup treatment.