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

Abstract

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. To describe the clinical and immunologic features of goat's and sheep's milk (GSM) allergy in patients who tolerated CM after CMOIT. 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. 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. 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.