What do I give a child who’s allergic to both cow’s milk and soy?

Unfortunately, some children are soy protein intolerant. As it happens, this is more common in kids who are allergic to cow's milk protein.

You might try using a protein hydrolysate infant formula such as Alimentum or Nutramigen for the next 2 weeks, because children are much less likely to be allergic to the protein in them. If they work, you can then experiment with other sources of calcium, protein, and fat for the future (perhaps rice milk). If they don’t work, your child may need an amino acid-based formula, such as EleCare or Neocate.