Objective: To understand the mechanism underlying the nasal congestive response to irritant challenge.

Methods: We exposed 22 subjects–8 with seasonal allergic rhinitis (SAR), 6 with perennial allergic rhinitis (PAR), and 8 normals–to chlorine (Cl2) gas (1.0 ppm x 15 min.) by nasal CPAP mask. Control exposures (filtered air) were carried out on separate days, with counterbalancing of exposure order. Nasal airway resistance (NAR) was measured in triplicate before and after the provocation sequence using active posterior rhinomanometry. For each subject, this experiment was repeated twice, after [double-blinded] pre-treatment with: 1) ipratropium bromide (IB) 0.6% nasal spray, and 2) vehicle. Results: As a group, allergic rhinitics (SAR+ PAR) showed greater [Cl2] exposure-related increases in NAR than did normals on placebo (vehicle) pretreatment days (p< 0.05). IB pre-treatment, however, did not have a systematic effect on Cl2-induced congestion. Conclusion: Cholinergic mechanisms do not appear to be responsible for the nasal congestive response to irritant provocation.