Sensitization to Human Milk

Schulmeister U, Swoboda I, Quirce S, et al. Clin Exp Allergy. 2008;38(1):60–68 PURPOSE OF THE STUDY. To analyze the specificity and possible biological relevance of immunoglobulin E (IgE) reactivity to human milk antigens in milk-allergic patients. STUDY POPULATION. Milk-allergic children and adults from different European countries with a positive case history, positive skin-prick reactions, and specific IgE to cow's milk extract were selected. METHODS. The specificity of IgE reactivity to cow's milk and human milk antigens was analyzed with sera from milk-allergic children and adults by immunoblotting. IgE cross-reactivity between milk antigens was studied by immunoblot inhibition experiments. To demonstrate that IgE reactivity to human milk antigens is not caused by alloreactivity or transmission of foreign antigens, genetically unrelated mothers’ milk samples were analyzed before and after intake of dietary milk products. Skin-prick tests were performed with cow's, sheep's, mare's, and human milk samples. RESULTS. IgE antibodies to human milk were found in >80% of the tested milk-allergic patients (n = 17). Cross-reactive IgE-reactive human antigens such as α-lactalbumin and non–cross-reactive human milk antigens were identified. Immunoblots showed IgE reactivity to antigens of the same molecular weights in each of the 4 milk samples from unrelated mothers. An immediate-type skin reaction could be elicited with human milk samples in 2 tested patients with IgE reactivity to human milk. CONCLUSIONS. IgE reactivity to human milk in milk-allergic patients may be caused by cross-sensitization and genuine sensitization, causing allergic symptoms. Sensitization to human milk is common in milk-allergic patients and may require diagnostic testing and clinical monitoring. REVIEWER COMMENTS. This is one of the first studies to have addressed the nature and biological relevance of IgE reactivity to human milk. The study demonstrated that sensitization to human milk is common in milk-allergic patients, but additional research is necessary, because it is unclear if patients with positive skin reactions suffered from clinically significant reactions to human milk. One may consider searching for the presence of IgE antibodies to human milk in children who have signs of allergy after breastfeeding. However, the benefits of breastfeeding, including its protective effect against early atopic diseases, must also be considered before advising dietary changes.