Allergy to goat’s and sheep’s milk in a population of cow’s milk–allergic children treated with oral immunotherapy*

Abstract

Background: Cow's milk oral immunotherapy (CMOIT) is a recognized treatment for persistent cow's milk (CM) allergy. However, further data are necessary on tolerance to milk from other mammals. Objective: To describe the clinical and immunologic features of goat's and sheep's milk (GSM) allergy in patients who tolerated CM after CMOIT. Methods: Fifty-eight CM-allergic patients who successfully underwent CMOIT in our department were evaluated using skin prick test (SPT), specific immunoglobulin (Ig) E determination, enzyme-linked immunoassay (ELISA), and controlled oral challenge to assess allergy to GSM. Statistical analysis was carried out to identify markers of allergy to GSM. Results: Fifteen of 58 (25.9%) patients were allergic to either goat's or sheep's milk or to both, as confirmed by a controlled positive oral challenge. Forty-seven percent of all positive oral challenges were classified as anaphylactic reactions. Specific IgE to CM casein, goat's whole milk, and sheep's whole milk was 13.2, 18.0, and 21.4 kU(A)/l in the group of GSM-allergic patients and 6.6, 6.5, and 6.5 kU(A) /l in the GSM-non-allergic patients (p < 0.05). Decision-making cut-off points based on sIgE for diagnosing symptomatic GSM allergy could not be determined. ELISA inhibition assays showed limited cross-reactivity (up to 77.2%) between CM casein and GSM casein in the group of GSM-allergic patients in contrast with almost 100% in GSM-not-allergic patients. Conclusion: We found a high prevalence (26%) of allergy to GSM in our population of CM-allergic children treated with oral immunotherapy. Therefore, tolerance to GSM should be assessed in order to provide accurate nutritional advice and minimize life-threatening accidental intake. Specific IgE to CM casein, goat's and sheep's whole milk is a good marker of this allergy. Although CM oral immunotherapy is a specific treatment for CM allergy, it may not be effective against allergy to the milk of other mammals.