Nasal and bronchial histamine responsiveness in pollen-exposed patients with seasonal rhinitis.

In a previous study, we found an increased nasal responsiveness as measured by rhinostereometry and histamine challenge out of season in a sample of 12 patients suffering mainly from hay fever. The aim of the present study was to investigate whether airway responsiveness in these patients was further increased after direct pollen exposure, after a single nasal pollen provocation as well as by repeated exposure during the pollen season. In spite of increased allergic symptoms, the basal degree of nasal mucosal swelling was unchanged before histamine challenge under these circumstances. After histamine challenge, nasal mucosal swelling was increased in the same way over the seasons. Also bronchial responsiveness was unchanged during the pollen season. It correlated to frequent sneezing following nasal histamine challenge during the season (p = 0.0071, r = -0.74). We interpret the results as an indication of a continuos airway inflammation regardless of season in these patients with pollen allergy, with acute symptoms added on direct exposure to the allergen.