Cow's milk protein-specific IgE concentrations in two age groups of milk-allergic children and in children achieving clinical tolerance

Background IgE-mediated cow's milk protein allergy (CMPA) is usually outgrown in children by the age of 3 years. The immunological responses to cow's milk proteins in children who achieve tolerance, in comparison with those who remain allergic, however, are not well described. Objective To compare the level of cow's milk protein-specific IgE among children with documented CMPA under the age of 3 years, another group over the age of 9 years (persistent allergy), and in another group of children in whom clinical tolerance developed. Methods Stored sera from children with CMPA were analysed for IgE antibodies specific for whole cow's milk, casein, whey, alpha-lactalbumin (ALA), beta-lactoglobulin (BLG), and bovine serum albumin (BSA) using the Pharmacia CAP System FEIA. Results Within each group of CMPA children, the concentration of specific IgE antibody to casein proteins was not significantly different from that to whey proteins. However, children in the group with CMPA over 9 years of age had significantly greater concentrations of whole milk (P=0.02) and casein-specific (P=0.04) IgE antibodies compared with the group of children with CMPA under age 3 years. Children under the age of 3 years had a higher median concentration of casein-specific IgE (20.2 vs. 5.5, P=0.04) than another group of 11 children (mean age 3.5years), who later lost their milk allergy. Out of 16 children who lost sensitivity to milk, 75% had milk-specific IgE levels below 14.31<U-A/L (median, 1.3 kU(A)/L). Conclusions Although a dominant allergenic milk protein fraction was not identified within either of the two age groups, those with persistent CMPA over age 9 years had significantly elevated levels of milk and casein-specific IgE compared with younger children with CMPA.