How do you feed a child that is lactose intolerant? Do foods without milk but with whey or casein cause problems?

Avoid lactose. The sugar in human and bovine (cow) milk is lactose and u avoid symptoms by avoiding lactose. Cheddar cheese, a bovine milk product has minimal lactose left in it after the transition to cheese. Other lactose free products like soy milk are available. A lactose intolerant kid can usually tolerate milk with added lactose enzyme that is sold under various names like "lactaid".