It seems to make intuitive sense -- if you are allergic to beef then you should stay away from cow's milk, right? Not necessarily. Although most food allergies are associated with animal proteins, there is rarely cross-contamination. That is, if you are allergic to eggs, you can still eat chicken; and if you are allergic to fish, you can still have a glass of milk [source: AAAAI]. Put simply, you are unlikely to experience a milk allergic reaction if you have a beef allergy. So go ahead, enjoy your milkshake with your soy burger! However, you may not need to resort to that soy burger. If you are allergic to beef, try eating game meat, which is lower in fat and higher in essential fatty acids than traditional beef. Game meat also does not cause as much damage to your intestinal tract compared to traditional beef [source: Food-allergy.org].
It is important to consider, however, that adult and child food allergies are not necessarily the same. In fact, one research study showed that 93 percent of children with a beef allergy also had a cow's milk allergy [Martelli et al.]. Therefore, the cross-contamination of cow's milk and beef proteins in children is common, so children with a beef allergy should avoid consuming milk and milk products. After puberty, an allergy test can determine if this cross-contamination is still present.
Although cross-contamination between two animal-related proteins is rare, it is not uncommon for people with milk allergies to experience allergy-related symptoms when eating beef. Processed meats sometimes contain milk ingredients for flavor enhancement or as a binding material. For example, milk is commonly used in the breading of chicken nuggets. Moreover, other types of processed meats, such as luncheon meat and hot dogs, commonly have milk as an ingredient [source: Food Standards Agency].