The concept of hypoallergenicity for atopy prevention.

Infancy represents the period in which an individual may be at the highest risk of sensitization. During the first year of life around 2.5% of neonates experience hypersensitivity reactions to cow's milk protein, which is highly associated with early exposure to cow's milk. Attempts to avoid sensitization in this very early period of life and to prevent allergic diseases focus on diets with reduced allergenicity and possibly on the induction of oral tolerance. Hydrolyzed infant formulas are characterized by a reduced allergenicity and thus recommended as substitute or supplementary to breastfeeding during the first 4-6 months of life for infants at high risk of developing atopic diseases. This concept of hypoallergenicity has been shown effective in clinical studies. Both partially and extensively hydrolyzed formulas have demonstrated a potential in protecting from allergic diseases, mainly atopic eczema and food allergy. The in vitro characterization of allergenicity by the degree of hydrolyzation and peptide size, however, does not necessarily predict the immunogenic effect in humans, as it could be shown that the preventive effect seems to be dependent on the process rather than on the degree of hydrolyzation, which could be best explained by a possible production of tolerogenic epitopes.