Abstract
BACKGROUND: Probiotics have proven beneficial in a number of immune-mediated and allergic diseases. Several human studies have evaluated the efficacy of probiotics in allergic rhinitis; however, evidence for their use has yet to be firmly established. The current systematic review seeks to synthesize the results of available randomized trials. METHODS: In a systematic review and meta-analysis, the Medline, EMBASE, and Cochrane Library databases were reviewed and randomized controlled trials (RCTs) were extracted based on defined inclusion criteria. The effect of probiotics on Rhinitis Quality of Life (RQLQ) scores, Rhinitis Total Symptom Scores (RTSS), as well as total and antigen-specific serum immunoglobulin E (IgE) levels were evaluated by meta-analysis. RESULTS: A total of 23 studies with 1919 patients were identified, including 21 double-blind RCTs and 2 randomized crossover studies. Multiple probiotic strains, study populations, and outcome measures were used in individual trials. Seventeen studies showed a significant clinical benefit from the use of probiotics in at least 1 outcome measure when compared to placebo, whereas 6 trials showed no benefit. Among the trials eligible for meta-analysis, the use of probiotics resulted in a significant improvement in RQLQ scores compared to placebo (standard mean difference [SMD] -2.23; p = 0.02). Probiotics had no effect on RTSS (SMD -0.36; p = 0.13) or total IgE levels (SMD 0.01; p = 0.94), although there was a trend toward a reduction in antigen-specific IgE (SMD 0.20; p = 0.06) in the placebo group compared to probiotic. CONCLUSION: Probiotics may be beneficial in improving symptoms and quality of life in patients with allergic rhinitis; however, current evidence remains limited due to study heterogeneity and variable outcome measures. Additional high-quality studies are needed to establish appropriate recommendations.