Eustachian tube obstruction (ETO) after histamine nasal provocation--a double-blind dose-response study.

Eustachian tube obstruction (ETO) has been reported to develop more frequently in subjects with allergic rhinitis (AR) than in subjects without AR after a single intranasal histamine challenge. The present double-blind crossover study was designed to confirm and extend this observation. In a pilot study, nebulization was demonstrated to be superior to insufflation in provoking ETO. Five subjects with AR and five subjects without AR were repeatedly challenged intranasally with nebulized normal saline or increasing doses of histamine (0.01, 0.1, 0.5, 1.0, 5, and 10 mg per nostril). Subjects with AR were selected on the basis of AR symptoms and IgE antibodies to allergens and were challenged in their nonallergy seasons. ETO was assessed by nine-step tympanometry and nasal airway resistance by anterior rhinomanometry before and after each challenge. Of nine ears in subjects with AR, ETO developed in five ears at 0.1 mg and in four ears at 0.5 mg. In contrast, in 10 ears of subjects without AR, ETO developed in two ears at 5 mg but did not develop in eight ears at doses as large as 10 mg. This test effectively discriminated subjects with AR from subjects without AR, groups that could not be similarly differentiated by nasal or skin responsiveness to histamine challenge. Saline challenges provoked ETO in three of nine ears of subjects with AR and in one of 10 ears of subjects without AR. These data suggest a hyperresponsiveness of the nasopharyngeal and/or tubal mucosa to histamine in subjects with AR that may predispose these patients to otitis media with effusion.