Effects of Probiotics on Allergic Rhinitis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Background The prevalence of allergic rhinitis has been estimated to range from 10 to 30% in adults and up to 40% in children. Probiotics have been tested as for this condition, but no census on which probiotic types are most effective. Objective Our aim of this study was to provide probiotic strain-specific evaluation for the treatment of allergic rhinitis. Methods Databases (PubMed, Google Scholar, and ScienceDirect) were searched (from inception to October 2020) to identify randomized controlled trials (RCTs) of probiotic treatments in allergic rhinitis patients. A systematic review was done comparing types of reported outcomes, clinical and immunological parameters and safety data. A meta-analysis was done for probiotics with at least two RCTs per probiotic strain(s) and sharing a common outcome. Results A total of 13 randomized, double-blind, placebo-controlled trials (N = 1591 participants) were included in the systematic review. Overall, 8 of 9 probiotic types alleviated at least one clinical symptom of allergic rhinitis. The meta-analysis results showed that, neither L. paracasei Lp33 (SMD = −1.61, 95% CI −4.67, 1.45) nor L. rhamnosus GG (SMD = −1.00, 95% CI −3.01, 1.00) had significant efficacy for reducing nasal symptom scores. Conclusions Our analysis showed probiotics produced a slight improvement in some clinical and immunological measurements on allergic rhinitis. Due to the diversity of outcome measurements and lack of sufficient trials for each probiotic strain, future trials are needed with similar study design and uniform outcomes to better compare the effect of probiotics on allergic rhinitis.