Almost everyone is allergic to cow's milk. That's why mammals breast feed. When you don't or can't breast feed, one thing missing is the immune system building colostrum found in early breast milk. No formula is healthy -- they are just the best we can do sometimes. But I'm guessing there must be something other than just cow milk allergy going on, since there are plenty of substitutes for that (the best being breast milk, but there's also goat milk, sheep's milk, etc.). But try asking your health professionals if supplemental colostrum might not be helpful if you can't breast feed.
Like the person above already mentioned, most of the world is allergic to cows milk or lactose intolerant. No other animal in the world eats another animals milk hut us. We are also the only species that drinks milk past infant stage. My father was fed on goats milk because of this same problem. You may be able to speak to your Dr about receiving donated breast milk from other mothers. They use this especially with premature babies but your son may be a good candidate. I wish you the best of luck with this!