Antihistamines have been reported to have antitussive actions in allergic rhinitis which may be due to an effect of the drug on the cough reflex. We have studied the effect on induced cough in normal volunteers. Ten volunteers inhaled capsaicin at concentrations between 0.78 and 200 microM, in increasing dose order, until they coughed more than five times. The challenge was performed three times before and three times each at 2 and 4 h after 120 mg terfenadine or matched placebo tablet in a double-blind, randomized, cross-over study. Neither affected the capsaicin cough challenge. Thus, any antitussive effect of terfenadine is more likely to be via an indirect mechanism such as inhibition of released histamine rather than on the cough reflex itself.