Anaphylactic reaction to goat's milk in a cow's milk-allergic infant.

Goat's milk has been used as a substitute for cow's milk in cow's milk-allergic individuals. It is currently advocated for this purpose in writings and internet resources directed at the lay person, and infant formula based on goat's milk is available in many countries. Clinically significant cross-allergenicity between cow's and goat's milk has been noted, but a life-threatening cross-reaction has not been reported. We describe a 4-month-old infant with immunologically documented cow's milk protein allergy but no prior exposure to goat's milk who developed anaphylaxis after the ingestion of commercial goat's milk. Subsequent skin prick testing demonstrated a specific reaction to goat's milk. Thus, the cross-allergenicity between cow's and goat's milk proteins can lead to life-threatening complications. Individuals allergic to cow's milk protein should avoid goat's milk and goat's milk products.