No effect of probiotics on respiratory allergies: a seven-year follow-up of a randomized controlled trial in infancy.

Background Supplementation with the probioticLactobacillus reuteri reduced the incidence of IgE-associated allergic disease in infancy. This treatment might therefore also reduce the risk of asthma and allergic rhinoconjunctivitis in school age. Objective To evaluate whether perinatal and infant supplementation withL.reuteri reduced the prevalence of respiratory allergic disease in school age and to explore whether this supplementation was associated with any long-term side effects. Methods A randomized, placebo-controlled trial with oral supplementation withL.reuteriATCC 55730 (1x10(8)CFU) during the last month of gestation and through the first year of life comprising 232 families with allergic disease, of whom 184 completed a 7-yr follow-up. The primary outcomes at 7yr of age were allergic disease and skin prick test reactivity (ClinicalTrials.govID NCT01285830). Results The prevalence of asthma (15% in the probiotic vs. 16% in placebo group), allergic rhinoconjunctivitis (27% vs. 20%), eczema (21% vs. 19%) and skin prick test reactivity (29% vs. 26%) was similar in the probiotic and placebo group. Growth indices and gastrointestinal symptoms were similar in the two groups. No severe adverse events were reported. Conclusion The effect ofL.reuteri on sensitization andIgE-associated eczema in infancy did not lead to a lower prevalence of respiratory allergic disease in school age. Thus, the effect ofL.reuteri on the immune system seems to be transient. Administration ofL.reuteri during the last weeks of gestation and in infancy was not associated with any long-term side effects.