Cow's milk protein is quite commune in infancy (2-3% in first year of age). Casein, beta-lactoglobulin and alpha-lactalbumin are the main allergens of cow's milk. The authors describe the immunological reaction involved in IgE synthesis and consequential inflammation after ingestion of cow's milk proteins and present soy and protein extensive hydrolysates as alternative diets for children with cow's milk allergy. Moreover, the authors present their studies on immunogenicity of hydrolysed formulae. At the end they suggest the therapeutic strategy in the cow's milk protein allergy.