Plain language summary
Allergic rhinitis (AR) is characterized by a nasal sensitive inflammation. Common symptoms of AR are nasal itching, sneezing, rhinorrhoea, and nasal congestion. In addition, some patients experience symptoms of allergic rhinoconjunctivitis, such as watery or itchy or red eyes. The aim of this study was to address the effect and safety of probiotics on AR and to explore the possible causes of between-study heterogeneity via subgroup. This study is a systematic review and meta-analysis of twenty-eight randomised controlled trials. Results showed that probiotics supplementation for patients with AR can ameliorate AR symptoms and improve the quality of life. Probiotics supplementation can correct the T helper cell 1/ T helper cell 2 balance. Furthermore, there was no significant change in overall or antigen-specific immunoglobulin E levels between probiotic-treated and placebo-treated subjects. Authors conclude that in spite of the positive results of some outcomes, there is weak evidence that probiotics have a potential benefit in the treatment of AR.
Abstract
Background: Probiotics have proven beneficial in a number of immune-mediated and allergic diseases. Several human studies have evaluated the efficacy and safety of probiotics in allergic rhinitis; however, evidence for their use has yet to be firmly established. Objective: We undertook a systematic review and meta-analysis aiming to address the effect and safety of probiotics on allergic rhinitis. Methods: We systematically searched databases [MEDLINE (PubMed), Embase, and the Cochrane Central Register of Controlled Trials] from inception until June 1, 2021. Qualified literature was selected according to inclusion and exclusion criteria, the data were extracted, and a systematic review and meta-analysis was conducted. Results: Twenty-eight studies were included. The results showed that probiotics significantly relieved allergic rhinitis symptoms (standardized mean difference [SMD], -0.29, 95% confidence interval (CI) [-0.44, -0.13]; p = 0.0003, I 2 = 89%), decreased Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) scores compared with the control group (SMD, -0.64, 95% CI [-0.79, -0.49], p < 0.00001, I 2 = 97%), and increased T helper cell 1(Th1)/Th2 ratio (mean difference [MD], -2.47, 95% CI [-3.27, -1.68], p < 0.00001, I 2 = 72%). There was no significant change in overall or specific IgE levels between probiotic-treated and placebo-treated subjects (SMD, 0.09, 95% CI [-0.16, 0.34], I 2 = 0%, and SMD, -0.03, 95% CI [-0.18, 0.13], p = 0.72, I 2 = 0%, respectively). Conclusions: To sum up, probiotic supplement seems to be effective in ameliorating allergic rhinitis symptoms and improving the quality of life, but there is high heterogeneity in some results after subgroup analysis and clinicians should be cautious when recommending probiotics in treating allergic rhinitis. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/, PROSPERO (CRD42021242645).
Methodological quality
Jadad score
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Not applicable
Allocation concealment
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