LONDON, Oct. 15 (UPI) -- British and Viennese scientists have found the relatedness of an animal food protein to a human protein determines whether it can cause an allergy.

    In theory, all proteins have the potential to become allergens. But scientists from Britain's Institute of Food Research and the Medical University of Vienna found the ability of animal food proteins to act as allergens depends on their evolutionary distance from a human equivalent.

   "This explains why people who are allergic to cow's milk can often tolerate mare's milk but not goat's milk", said Clare Mills of the Institute of Food Research. "Proteins in horse milk are up to 66 percent identical to human milk proteins, while known allergens from cows and goats are all less than 53 percent identical to corresponding human proteins.

   "Overall we found that only an animal food protein that is less than 54 percent identical to a human equivalent could become allergenic".

   The study is to be published Tuesday in the online issue of the Journal of Allergy and Clinical Immunology.

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