It's a true milk allergy. I can tolerate some, but it would be an issue during exercise. I get congested, I hack up thick phlegm, my HR goes up, etc. I've tried whey protein products and I do react to them - apparently whatever the specific protein(s) are that I'm allergic to are contained in the whey fraction.

I never thought of it that way before actually... it does explain why I can tolerate cheese somewhat better than whole milk products, even though I'm not lactose intolerant.

Egg white protein sounds like a possibility. I'll look into it, thanks!