Cow's milk allergy (CMA) is the most common food allergy in young children but is uncommon in adults. This food allergy presents with a wide range of clinical syndromes due to immunologic responses to cow's milk proteins that can be immunoglobulin E (IgE) and/or non-IgE mediated. CMA does not include other adverse reactions to milk, such as lactose intolerance, which are non-immune mediated.
Issues of cross-reactivity among milk of different mammalian species (such as sheep and goat) are addressed here. This topic also reviews various aspects of management of milk allergy, including instructions about avoidance of milk protein, replacement of milk with alternative protein and calcium sources, education in the proper management of accidental exposures, and monitoring for resolution of the allergy. The epidemiology, pathogenesis, clinical features, and diagnosis of milk allergy are discussed separately. Most patients with cow's milk allergy (CMA) do not tolerate milk from sheep and goats, and they are unlikely to tolerate milk from deer, ibex, and buffalo as well. However, some patients with CMA may tolerate milk from other mammals, such as camels, pigs, reindeer, horses, and donkeys.
Mammals that are phylogenetically related, such as cow and water buffalo, sheep and goat, and horse and donkey, have similar milk protein expression. In vitro studies have shown extensive cross-reactivity between milk from cows, sheep, and goats but only weak cross-reactivity with proteins from donkeys and mares. Significant amino acid sequence homology and a resulting high rate of clinical cross-reactivity between milk from ruminants (eg, approximately 90 percent of children with immunoglobulin E [IgE]-mediated CMA react to goat's milk) make milk from sheep and goats inappropriate feeding alternatives for most CMA individuals. However, some patients with primary goat's or sheep's milk allergy may tolerate cow's milk
Co-sensitization assessed by skin testing to deer's, ibex's (wild mountain goat), and buffalo's milk is common in patients with CMA, but positive skin tests to camel's and pig's milk are uncommon. There is also only partial cross-reactivity between cow's milk and reindeer's milk beta-lactoglobulins in patients with CMA. However, studies on clinical tolerability of these alternative mammalian milks are missing.