Effects of the supplementation of single and multi-strain probiotics, alone or in combination with other treatments, on asthma in children: A systematic review of the randomized, placebo-controlled clinical studies

Gut microbiota plays an important role in maintaining respiratory health while providing protection against
respiratory illnesses. However, the clinical role of probiotic strains in prevention and treatment of early-onset
asthma is still debated. The present study aims to systematically review the available literature on the efficacy
of probiotic supplementation, either alone or in combination with other treatments, in managing children with
asthma. An electronic search was conducted across multiple databases including PubMed, Web of Science, and
EMBASE. The articles reported in English, regardless of year of publication, were reviewed by independent
authors for inclusion assessment. Randomized controlled studies evaluating the efficacy of probiotics in children
with asthma were included in the study. Of the 203 articles reviewed, 16 were selected and summarized to
provide a consistent review, and of these, eight studies reported the anti-asthmatic effects of the treatment with
single and multi-strain probiotics alone, seven reported the use of probiotic strains in combination with other
treatments, and one was a follow-up study. While some of the studies reported are well conducted and with
promising results, no cumulative significant impact was seen for probiotic supplementation on disease parameters
of asthma in children. However, the available literature is not sufficient to draw any solid conclusion about
the possible use of probiotics in children with asthma, and it is necessary to expand this literature by conducting 

more well-designed randomized clinical trials to assess the effects of probiotic strains in children with asthma or
carrying a high-risk of asthma.