The aim of the present study was to evaluate the IgE-mediated response as a predictable index of immunosensitization to different types of feeding (breast milk, adapted formula, soya formula and serum protein hydrolyzate formula) in the first days of life. The study population included 231 newborns (128 males and 103 females). There was a family history of atopy (at least 1 parent with an atopic disease) in 116 subjects at risk for allergy. 115 newborns were without any family history of atopy. The results showed significantly higher total IgE levels on the 4th day than in cord serum in the whole group of newborns. The same result was obtained comparing subjects at risk and controls separately. No significant difference was detectable between serum IgE levels in the cord blood of the four groups. Conversely, a significant increase in IgE levels between cord and 4th day blood in soya-fed and adapted-formula-fed babies was noticed. This increase did not occur in neonates fed breast milk and serum protein hydrolyzate.