Abstract: The present invention provides a probiotic, Lactobacillus paracasei NCC 2461, i.e. ST11, for use by administration to expectant females and/or lactating mothers, and to their progeny for the reduction or prevention of the development of allergic immune responses in progeny. A daily dose of ST11 is administered to a pregnant woman for at least two weeks before delivery and, after delivery, the daily dose of ST11, is administered to the lactating mother or the newborn infant for at least two months, either directly or via the mother's milk. The infant immune responses to allergens are thus reduced, resulting in a “dampened” allergic response. Thus allergy, including atopy, may be prevented in the progeny.