Probiotics for the treatment of allergic rhinitis and asthma: systematic review of randomized controlled trials

Objective: To evaluate the clinical evidence for the use of probiotics as a therapeutic modality for allergic rhinitis (AR) and asthma. Data Sources: PubMed was searched to identify randomized controlled trials (RCTs) that studied the effects of probiotics on AR (n = 12) and asthma (n = 4). Study Selection: RCTs that studied the effects of probiotics administration on the treatment but not the prevention of AR and asthma were selected for inclusion in this review. Results: Nine of the 12 RCTs that evaluated clinical outcomes in AR showed an improvement due to the use of probiotics. All the RCTs that studied perennial AR showed lower symptom scoring and medication use with the use of probiotics compared with placebo. Also, 5 of the 8 RCTs that referred to seasonal AR suggested an improvement in clinical outcomes. Nine RCTs that reported various immunologic measurements of allergy found no significant probiotic effects. The RCTs that studied the effect of probiotic administration on the treatment of asthma showed no positive effects. Conclusions: Probiotics may have a beneficial effect in AR by reducing symptom severity and medication use. Many more good-quality studies are needed to resolve this issue.