In a study on prevention of allergy in newborns, L. reuteri ATCC 55730 reduced the incidence of IgE-associated allergic disease in infancy. This treatment might therefore also reduce the risk of asthma and allergic rhino‑conjunctivitis in school age, which this follow-up study set out to investigate. It also evaluated whether this supplementation was associated with any long-term side effects. The age at follow-up was 7y.

In the 2007 double-blind, and placebo controlled trial, 232 infants were randomised and 188 completed. 184 children took part in the follow-up, whereof 94 in the L. reuteri group and 90 in placebo group.  

For the allergic disease outcomes there were no differences between groups: The prevalence of asthma was 15% in the L. reuteri vs. 16% in placebo group; allergic rhino conjunctivitis: 27% vs. 20%; eczema: 21% vs. 19%; skin prick test reactivity: 29% vs. 26%. 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.