The present invention is in the field of prophylaxis of allergies, and relates specifically to primary prevention of atopic diseases by administering probiotic bacteria, beneficial microbes of the healthy gut flora, pre- and postnatally to children at high risk of atopic diseases. In an embodiment, probiotic bacteria are administered to a pregnant woman at least two weeks before infant delivery and after delivery, probiotic bacteria are administered to the newborn infant for at least two months. The amount of probiotic bacteria administered is about 1.times.10.sup.8 to about 1.times.10.sup.10 colony forming units of the probiotic bacteria.