Because food allergy is frequent and severe, all possible means should be used to try to prevent its manifestations or at least to delay them until the child is older and stronger and therefore better able to follow an exclusion diet. The capacity of breast-feeding for preventing food allergy has been challenged in the past, but a consensus seems to be emerging now that breast-feeding can indeed prevent food allergy if it is started at birth and is exclusive for at least 4, and preferably 6, months. In the most "at-risk" babies the breast-feeding mother should try to eliminate the most potent allergens (eggs, fish, soya, nuts, and cow's milk) from her diet. If a substitute or a complement to breast milk is necessary, neither goat's milk nor soy milk formula are adequate. Heat treatment alone will not be sufficient to make cow's milk hypoallergenic. Only a combination of protein hydrolysis and managed heat treatment can make cow's milk hypoallergenic and retain its nutritional value. This nutritional value should be assessed by animal studies and also by studying infant growth. The hypoallergenicity of a formula can be studied in vitro and with animal tests, but only clinical trials on human infants will prove its efficacy.