Preventive effect of nasal filters on allergic rhinitis: A randomized, double-blind, placebo-controlled crossover park study.

Background A recently reported small, out-of-season environmental exposure unit study found nasal filters to be efficacious in preventing seasonal allergic rhinitis (AR). However, nasal filters still need to show efficacy in a natural setting in a regular pollen season. Objective We sought to evaluate the efficacy of nasal filters (Rhinix; Rhinix ApS, Aarhus, Denmark) for the prevention of symptoms related to seasonal AR. Methods The trial was a single-center, randomized (1:1), double-blind, placebo-controlled crossover clinical trial (NCT02108574) conducted over 2 days in the main grass pollen season in June 2014 in Aarhus, Denmark, on 65 adults with proven grass allergy. A total nasal symptom score (TNSS) consisting of blocked nose, runny nose, nasal itching, and sneezing was used to evaluate symptoms. The difference in daily ∑ TNSS (the sum of 13 ratings) was the primary outcome measure. The difference in maximum TNSS (highest score, 13 ratings) was also evaluated. Results The nasal filters significantly reduced daily ∑ TNSSs ( P  = .03) and maximum TNSSs ( P  = .03) compared with placebo. Median relative reductions were 40% for daily ∑ TNSSs ( P  = .02), 43% for maximum TNSSs ( P  = .004), 83% for daily ∑ sneezing ( P  = .001), 75% for daily ∑ watery eyes ( P  = .02), and 53% for daily ∑ runny nose ( P  = .005) when compared with placebo. The nasal filters were well tolerated, and no serious adverse events were recorded. Conclusion Statistically significant and clinically relevant reductions were achieved for the primary outcome measure of daily ∑ TNSS, for maximum TNSS and for a subset of individual symptoms. The results support the preventive role of nasal filters for managing seasonal AR.