Tolerance to extensively heated milk in children with cow's milk allergy

Background: Cow's milk allergy is the most common childhood food allergy. Previously we noted that children who outgrew their milk allergy had milk-specific IgE antibodies primarily directed against conformational epitopes; those with persistent milk allergy also had IgE antibodies directed against specific sequential epitopes. Objective: Because high temperature largely destroys conformational epitopes, we hypothesized that some children with milk allergy would tolerate extensively heated (baked) milk products. Methods: Children with milk allergy were challenged with heated milk products; heated milk-tolerant subjects were subsequently challenged with unheated milk. Heated milk-tolerant, unheated milk-reactive subjects ingested heated milk products for 3 months and were then re-evaluated. Immune responses were assessed in all subjects; growth and intestinal permeability were followed in heated milk-tolerant subjects. Results: One hundred children (mean age, 7.5 years; range, 2.1-17.3 years) underwent heated milk challenges. Sixty-eight subjects tolerated extensively heated milk only, 23 reacted to heated milk, and 9 tolerated both heated and unheated milk. Heated milk-reactive subjects had significantly larger skin prick test wheals and higher milk-specific and casein-specific IgE levels than other groups. At 3 months, subjects ingesting heated milk products had significantly smaller skin prick test wheals and higher casein-IgG(4) compared with baseline; other immunologic parameters, growth, and intestinal permeability were not significantly different. Heated milk-reactive subjects had more severe symptoms during heated milk challenge than heated milk-tolerant subjects experienced during their unheated milk challenge. Conclusion: The majority (75%) of children with milk allergy tolerate heated milk.