Nineteen children with IgE-mediated allergy associated with strongly positive prick skin tests and RASTs to peanut or cow's milk and/or egg were studied. Seventeen of the children had been breast fed, ten had been exclusively breast fed for a minimum of 5 months. Reactions to these foods occurred on first exposure to the food in all but one instance, suggesting that in 18 instances sensitization had occurred antenatally or via the breast. A retrospective inquiry indicated that most of the mothers had had a generous intake of the food(s) to which their children were sensitized, but mothers of sensitized children did not consume more of these foods than the mothers of non-sensitized children; moreover, avoidance of the foods (peanut in two instances and egg in one) did not ensure freedom from sensitization to peanut and/or egg. Breast feeding by itself cannot be guaranteed to protect against the development of food allergy.