This web site explains about sensitivity to cow's milk proteins in allergic babies,
http://www.kellymom.com/babyconcerns...nsitivity.html
“A significant percentage of babies with cow's milk protein allergy will also react to soy. Most dairy-allergic babies will also react to goat's milk or sheep’s milk. Some will also react to beef.”
If your baby is likely to be allergic to cow’s milk protein it might be best to delay not just cow’s milk but also soy milk, other dairy products and beef.
Best wishes,
Barb