Peripheral blood mononuclear cell proliferative responses and interferon-gamma production to anti-CD3, cat fur extract, betalactoglobulin and ovalbumin were determined at birth in a group of 34 babies born to families where at least one parent was atopic. The development of atopic eczema with positive allergy skin-prick tests to cows' milk and egg at 1 year of age, where the symptoms improved on an egg and milk-free diet, was significantly associated with raised proliferative responses and defective IFN-gamma production to stimulation with betalactoglobulin with a trend for similar responses to ovalbumin. This was not observed in those who did not develop atopic eczema or those with atopic eczema not associated with foods. Responses to cat fur extract were not significantly different between those with and without atopic eczema. This has important implications for the prediction at birth, not only of the probability of being allergic, but also of the specific allergens which will cause problems. The implementation of specific targeted allergen avoidance during the critical period in infancy, therefore, should be more easily applied and should facilitate attempts to prevent disease.