Reflex activation in allergen-induced nasal mucosal vascular reactions

Subjects with allergic rhinitis were challenged unilaterally with diluent and increasing doses of allergen. Challenge with the highest dose of allergen was also carried out after topical anesthesia of the nasal cavity using lidocaine. In the contralateral, unprovoked nasal cavity the mucosal blood flow was determined using the 133Xenon wash-out technique and the nasal airway resistance was determined by rhinomanometry before and after challenge. Nasal symptom scores were estimated 15 min after each challenge. Blood flow in the nasal mucosa in the unprovoked right nasal cavity decreased in a dose-dependent manner for th two highest doses of allergen where a reduction of 21% (p less than 0.05) and 26% (p less than 0.01) was obtained. Nasal airway resistance increased somewhat after the highest dose (p greater than 0.05). Topical anesthesia in the provoked nasal cavity inhibited the decrease in blood flow in the unchallenged nasal cavity. These findings suggest that the changes in the tone of the resistance vessels, but not the capacitance vessels, which are induced by allergen, are largely reflex-mediated.