We investigated the prevalence of bronchial hyperreactivity and atopic state in patients with chronic cough to see the cause and clinical significance of those factors in chronic cough.

We studied 92 individuals who had presented with paroysmal cough over 3 weeks without dyspnea or wheezing. Methacholine bronchial provocation test and allergic skin test with paranasal sinus X ray, symptoms, serum lgE levels and peripheral eosinophils were measured and analyzed.

1) Forty eight percent of patients showed positive hyperreactivity to methacholine provocation, 11 percent had postnasal drip syndrome and 9 percent had both of them, Three precent of patients were thought to have gastroesophageal reflux. However 29% has do specific causes for their cough.

2) Forty four percent of patients were atopic patients and others were non-atopics. There were no significant differences of symptom score, serum lgE levels and peripheral eosinophil count between the two groups.

3) Sixty two percent of atopic patients and 40 percent of non-atopic patient were cough variant asthma with positive reaction to methacholine provocation test. However there was no significant difference of mean PC20 of methacholine between the two group.

These results indicated that airway responsiveness and atopic started are important factors for chronic cough. However they were not predictable on the basis of clinical and ordinary laboratory findings.