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

BACKGROUND: Supplementation with the probiotic Lactobacillus 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 with L. 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 with L. reuteri ATCC 55730 (1 × 10(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 7 yr of age were allergic disease and skin prick test reactivity (ClinicalTrials.gov ID 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 of L. reuteri on sensitization and IgE-associated eczema in infancy did not lead to a lower prevalence of respiratory allergic disease in school age. Thus, the effect of L. reuteri on the immune system seems to be transient. Administration of L. reuteri during the last weeks of gestation and in infancy was not associated with any long-term side effects.