Chronic cough is the only symptom of eosinophilic bronchitis (EB). There is considerable overlap between EB and atopic cough. To investigate the antitussive effects of a histamine H1-recetor antagonist, epinastine hydrochloride (epinastine, CAS 80012-43-7, Alesion; 20 mg/day, once daily), cough scores, pulmonary function, capsaicin cough threshold, and bronchial hyperresonsiveness (BHR) to methacholine (MCh) were evaluated before and after a 4-week treatment with epinastine in patients with EB. In the epinastine group, the cough scores were decreased significantly (18.3 +/- 6.1 in week 1, 17.4 +/- 6.7 in week 2, 15.1 +/- 6.2 in week 3, 14.0 +/- 4.8 in week 4) in comparison with the value of 35.3 +/- 8.7 in week -2). The cough threshold for capsaicin improved from 1.70 +/- 3.04 micromol/l to 12.7 +/- 17.6 micromol/l in the epinastine group (p < 0.05; baseline vs. week 4) The bronchial hyperresponsiveness to MCh (Dmin) did not change significantly either in the epinastine or the placebo groups. The morning and evening peak expiratory flow rate (PEFR, L/min) did not change from the baseline period in either the epinastine or the placebo groups. These results suggested that epinastine may be useful for treating patients with EB and that histamine H1-receptor is related to the pathophysiology of coughing in EB.