Upper and lower airway hyperreactivity in recurrent croup.

Seventeen children with recurrent croup, who had their last episode within the previous 12 months, were evaluated clinically by allergy skin tests, pulmonary function tests, and a histamine inhalation challengae. Fourteen showed airway hyperreactivity. Flow-volume loops were obtained after a positive histamine response and compared with post histamine tracings of children with asthma and health control subjects. Children with recurrent croup as well as those with asthma showed a significantly greater fall in maximal expiratory flow rates than that shown in healthy control subjects. Those recurrent croup also had a significantly greater fall in maximal inspiratory flow rates when compared to those with asthma and to the control subjects. A specific type airway hyperreactivity suggestive of involvement of both upper and lower respiratory tract was seen in children with recurrent croup.