Anaphylaxis to goat/sheep's milk in a 4-year-old boy tolerant to cow's milk.

Immune-mediated reactions to dairy products may vary depending on the mammalian source. We present a case of anaphylaxis to goat/sheep's milk with tolerance to cow's milk. A 4-year-old boy of Eastern European descent presented with gastrointestinal and respiratory symptoms within minutes after eating a goat/sheep's milk-derived food product. The tryptase level measured 1 hour post initial symptoms and 1 month after the allergic reaction were 14.6 µg/L and 5.1 µg/L, respectively (norm: 0.0-13.5 µg/L), confirming the diagnosis of anaphylaxis. A skin prick test performed 1 month after the reaction was highly positive for goat/sheep's milk, but negative for cow's milk. Skin prick tests may establish a life-threatening goat/sheep's milk allergy. Goat/sheep's milk allergy should always be considered in cow's milk-tolerant patients who present with an allergic reaction to dairy products, or when undergoing/have completed of oral immunotherapy for cow's milk allergy. © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.