The results could not confirm LGG as an effective treatment of AD in infancy. However, there might still be subgroups of patients suitable for a probiotic intervention. In particular, the role of IgE‐mediated sensitization as a prerequisite for treatment success remains to be studied. Due to a broad range of prebiotic and probiotic formulas and/or foods it may be difficult to detect therapeutic effects unless particular care is taken to eliminate bias. This evidence concerns the gene IGHE and Alzheimer disease.