Efficacy of Capsaicin for Non-allergic Rhinitis: An Updated Systematic Review and Meta-analysis.

Non-allergic rhinitis (NAR) is a prevalent condition with limited effective treatments. Capsaicin, an agonist of the transient receptor potential vanilloid subfamily 1 (TRPV1) receptor, has emerged as a potential therapeutic option for NAR by targeting heightened nasal reactivity. This systematic review and meta-analysis, conducted in accordance with PRISMA guidelines and registered on PROSPERO, evaluated the efficacy of capsaicin for NAR treatment. Nine studies with placebo-controlled group were included, with primary outcomes assessed as total nasal symptom scores (TNSS), visual analog scale (VAS) scores, and the proportion of therapeutic responders. Meta-analysis revealed significant improvements in TNSS and VAS scores, along with a higher proportion of therapeutic responders in patients receiving capsaicin treatment compared to placebo. While some studies demonstrated reductions in substance P levels and TRPV1 expression after capsaicin treatment, further investigation is warranted. This meta-analysis provides preliminary evidence suggesting that capsaicin treatment holds promise for alleviating symptoms in patients with NAR. However, the limited number of studies and methodological heterogeneity necessitate larger and more rigorously designed clinical trials with standardized methodologies and advanced diagnostic techniques to establish their definitive roles in clinical practice.