Nasal reactivity to histamine and methacholine: two different forms of upper airway responsiveness.

In 44 subjects (healthy controls and patients with allergic, non-allergic or infectious rhinitis) we compared nasal histamine and methacholine responsiveness. A weak correlation between histamine- and methacholine-induced secretion was found (r = 0.34; p = 0.02), in contrast to the highly significant association between secretion and sneezes induced by histamine (r = 0.78; p < 0.0001). Our observations suggest that histamine and methacholine responsiveness represent different forms of upper airway hyperreactivity. The contribution of glandular responsiveness as measured by methacholine challenge and the involvement of irritant receptors or reflexes as measured by histamine provocation may vary between individuals.