Evidence Synthesis of Probiotic Supplementation for Allergic Rhinitis in Adults: A Systematic Review and Network Meta-Analysis.

BackgroundProbiotics are increasingly explored as a potential adjunctive treatment for allergic rhinitis, a condition affecting approximately one in five adults worldwide. Despite distinctive age-related differences in gut microbiota composition, immunologic characteristics, and clinical profiles, no previous systematic review has comprehensively evaluated immunological and inflammatory markers, as well as the clinical efficacy and safety of probiotic supplementation exclusively in adult patients with allergic rhinitis. This study aimed to fill this evidence gap.MethodsAccordingly, eligible studies were identified by searching PubMed and Embase, supplemented by manual screening. After data extraction, a systematic review with trial sequential analysis and Bayesian network meta-analysis was performed.ResultsIn total, 68 RCTs from 63 publications were included, involving 4901 adult participants, with 55 outcomes extracted for analysis. The pooled results showed that probiotic supplementation significantly improved clinical symptom severity, including rhinorrhea (MD, -0.19; 95% CI, -0.28 to -0.10; P < 0.001), nasal itching (MD, -0.23; 95% CI, -0.34 to -0.11; P = 0.001), nasal congestion (MD, -0.18; 95% CI, -0.24 to -0.11; P < 0.001), sneezing (MD, -0.17; 95% CI, -0.27 to -0.06; P = 0.003), ocular itching (MD, -0.17; 95% CI, -0.28 to -0.06; P = 0.007), total nasal symptom severity (MD, -1.50; 95% CI, -2.33 to -0.66; P = 0.001), and overall quality of life (MD, -0.30; 95% CI, -0.46 to -0.13; P = 0.002). However, no significant effects were observed on immunological and inflammatory outcomes. Multi-strain formulations, Bifidobacterium longum, and Bifidobacterium lactis showed consistently high rankings across several outcomes; however, these rankings should be interpreted cautiously given the lack of direct head-to-head comparisons between probiotic formulations.ConclusionOverall, the study demonstrated that probiotic supplementation may provide small clinical benefits with a favorable safety profile in adults with allergic rhinitis, supporting the role of probiotic supplementation as an adjunct rather than a replacement for standard treatment.