Relationship between recurrent croup and airway hyperreactivity.

The relationship between recurrent croup and bronchial asthma was evaluated by measuring bronchial hyperreactivity (methacholine challenge), physiologic parameters of upper airway obstruction, and skin response to environmental allergens. Patients with recurrent croup (n = 10) had a significantly higher degree of airway hyperreactivity and atopy than healthy children (n = 15), but significantly less than the patients with bronchial asthma (n = 30). No physiologic signs of upper airway obstruction could be detected at rest or following methacholine. It is suggested that bronchial asthma and recurrent croup share a few characteristics.