Clinical Effects of Polyphenolic Compounds on Allergic Rhinitis: A Systematic Review and Meta-Analysis.

BACKGROUND: Polyphenolic compounds (eg, catechins or quercetin) may reduce hypersensitivity and allergic symptoms, but clinical evidence remains inconsistent. OBJECTIVE: To evaluate the therapeutic potential of polyphenolic compounds for managing allergic rhinitis (AR). METHODS: A systematic review and meta-analysis of randomized controlled trials (RCTs) assessed the effects of polyphenolic compounds on AR symptoms and quality of life (QoL). RESULTS: Thirteen RCTs (823 participants) were included: 7 enrolling patients with seasonal AR and 6 with perennial AR. In seasonal AR, polyphenolic compounds significantly reduced total nasal symptom scores (standardized mean difference [SMD] = 0.75, P = .0001; I2 = 52.8%), sneezing (SMD = 0.58, P = .0042; I2 = 45.6%), and nasal itching (SMD = 0.54, P = .011; I2 = 41.7%). In perennial AR, total nasal symptom scores improved, whereas individual symptoms were inconclusive. The combined analysis of seasonal and perennial AR, along with a sensitivity analysis excluding 2 outlier trials, yielded a more conservative and robust estimate, showing reductions in total nasal symptom scores (SMD = 0.73, P < .0001; I2 = 38.1%), nasal obstruction (SMD = 0.50, P = .0003; I2 = 36.4%), and sneezing (SMD = 0.57, P < .0001; I2 = 25.7%). Overall certainty of evidence for key nasal symptom outcomes was low to very low due to inconsistency and risk of bias. Effects on QoL were not significant. CONCLUSION: Polyphenolic compounds may serve as a complementary option for alleviating nasal symptoms in patients with AR, but findings should be interpreted cautiously. Future large-scale, rigorous RCTs are needed.