Allergy to the heat-labile proteins alpha-lactalbumin and beta-lactoglobulin in mare's milk

Background: Allergy to mare's milk is rare. Recently however, mare's milk has been recommended for treatment of various ailments by practitioners of ''alternative medicine,'' and it is available in health food stores. Objective: We report a case of allergic reaction to mare's milk in a 51-year-old woman wile was able to tolerate cow's milk. Methods: The protein composition of mare's milk was determined by methods based on measurement of nitrogen content. The patient underwent prick and intracutaneous tests with commercially available bovine milk proteins and several mare's milk preparations, including mare's milk granulate and boiled mare's milk. RAST and immunoblotting were also performed. Results: Results of skin testing and RAST with cow's milk were negative but demonstrated an IgE-mediated allergy to mare's milk. Immunoblotting revealed two allergen bands with molecular weights of 16 and 18 kd, most likely representing the whey proteins alpha-lactalbumin and beta-lactoglobulin. The bands disappeared after the mare's milk was boiled indicating that the proteins are heat-labile. Conclusion: The results of this study demonstrate the existence of an IgE-mediated mar e's milk allergy caused by low molecular weight hear-labile proteins, most likely alpha-lactalbumin and beta-lactoglobulin, which do not cross-react with the corresponding whey proteins in cow's milk.