Comparative study of histamine and exercise challenges in asthmatic children.

Fifty asthmatic children were tested with both a standardized treadmill exercise and a histamine inhalation on 2 separate days. Ninety per cent had a positive response to histamine, whereas 74 per cent had demonstrable exercise-induced bronchoconstriction. There was a close relationship between responsiveness to histamine and exercise, because all patients who responded to histamine had exercise-induced bronchoconstriction. Eight children (16 per cent) responded to histamine only. Although prechallenge pulmonary function has an effect on the incidence of exercise-induced bronchoconstriction, it does not appear to influence the responsiveness to histamine. Therefore, when provocation testing is being done for the purpose of diagnosing asthma, histamine is preferable to exercise.