A nutritional composition comprising a partially hydrolysed milk protein having a degree of hydrolysis between 15 and 25% and 50 to 1000 nanograms of TGF-β per 100 ml of ready to consume composition and methods for the primary prevention of allergic reactions to newly introduced dietary protein at weaning and the prevention of development of atopic diseases in a young mammal at weaning comprising feeding to the young mammal a therapeutic amount of the composition are disclosed.