Importance: Atopic dermatitis (AD) is a highly prevalent condition that may be associated with an altered gastrointestinal microbiota that promotes an immune environment more susceptible to allergic disease. Synbiotics, a mixture of prebiotics and probiotics, have been used for the prevention and treatment of AD.
Objective: To investigate the efficacy of synbiotics for primary prevention and treatment of AD.
Data sources: PubMed/MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, and the CAB Abstracts Archive searchable database were searched from the inception of all databases to October 15, 2015, with no language restrictions.
Study selection: We included all published randomized clinical trials of synbiotics for prevention and/or treatment of AD. To be included, a publication needed to clearly define the intervention as oral administration of synbiotics (combination of probiotics and prebiotics) and must have included an assessment of AD disease severity, such as the Severity Scoring of Atopic Dermatitis (SCORAD) index, or the incidence of AD as an outcome measure. Only 8 of 257 initially identified studies (3%) met selection criteria.
Data extraction and synthesis: Data extraction was independently done by multiple observers and cross-checked to avoid errors. The quality of the selected studies was critically examined following the Cochrane guidelines. Data were pooled using a random-effects model.
Main outcomes and measures: The primary outcomes were the SCORAD index (treatment studies) and the relative risk of AD (prevention studies). The hypothesis was formulated before data collection.
Results: A total of 257 abstracts were screened to identify 6 treatment studies (369 children enrolled; aged 0 months to 14 years) and 2 prevention studies (1320 children enrolled; up to age 6 months in one study and term neonates aged <3 days in the other). From the 6 treatment studies included for random-effects meta-analysis, the overall pooled change in SCORAD index in those treated with synbiotics at 8 weeks of treatment was -6.56 (95% CI, -11.43 to -1.68; P = .008). Heterogeneity was significant (I(2) = 77.1%; P = .001). Subgroup analysis showed that the beneficial effect was significant only when using mixed strains of bacteria (weighted mean difference, -7.32; 95% CI, -13.98 to -0.66; P = .03) and when used in children aged 1 year or older (weighted mean difference, -7.37; 95% CI, -14.66 to -0.07; P = .048). From the 2 prevention studies included, the pooled relative risk ratio of AD in those treated with synbiotics compared with placebo was 0.44 (95% CI, 0.11 to 1.83; P = .26).
Conclusions and relevance: This meta-analysis shows evidence that supports the use of synbiotics for the treatment of AD, particularly synbiotics with mixed strains of bacteria and for children aged 1 year or older. Further studies are needed to evaluate the effectiveness of synbiotics for primary prevention of AD.