Crossed radioimmunoelectrophoresis (CRIE) was used to study the presence of scrum IgE against antigenic components of Cow milk in 21 selected milk‐allergic patients. The amount of each IgE specificity was estimated by a scoring system. The milk‐allergic children had mainly IgE against α‐lactalbumin, β‐lactoglobulin, albumin and immuno‐globulin, the four major proteins of bovin whey as well as IgE against three cascin components. A serum pool from 1000 normal adults had IgE against the same whey protein, but in smaller amounts, and no IgE against the casein components. Eight cow milk‐based formulae, commonly used for infant feeding, and goat milk were studied by the same method. It was found that six of the milk substitutes did not differ significantly from cow milk in antibody binding, but the two hydrolysed casein products. Nutramigen® and Pregestimil®, consisted of such small molecules that the rabbit antisera could not precipitate the Indrolysed proteins in the gels on the CRIE plates. It was therefore not possible to study their IgE binding, if any,