Background: Immunoglobulin E-mediated allergy to cow’s milk protein represents a major problem for infants who are not breast fed. A search for substitute milks revealed a cross-allergenicity to milk derived from goat and sheep but not to milk from a mare. We noted that the cow, goat and sheep species are both artiodactyls and ruminants, defining them as kosher animals, in contrast to the mare.

Objectives: To determine whether patients with IgE[1]-mediated cow’s milk allergy are cross-sensitized to milk from other species such as the deer, ibex, buffalo, pig and camel.

Methods: Patients with a clinical history consistent with IgE-mediated cow's milk protein allergy were tested by skin prick test to validate the diagnosis. They were then evaluated by skin-prick test for cross-sensitization to milk-derived proteins from other species.

Results: All patients allergic to cow's milk tested positive by skin-prick test for cross-reactivity to deer, Ibex and buffalo (n=24, P = 0). In contrast, only 5 of the 24 patients (20.83%) tested positive to pig milk and only 2 of 8 (25%) to camel’s milk. Cross-sensitization to soy milk was noted in 4 of 23 patients (17.39%), although they all tolerated oral ingestion of soy-containing foods.

Conclusions: A significant cross-sensitization to milk proteins derived from kosher animals exists in patients allergic to cow's milk protein, but far less so compared to the milk proteins from non-kosher animals tested. Patients with proven IgE-mediated allergy to cow’s milk can utilize the above findings to predict suitable alternative sources of milk.