5kg has a good point. I'm lactose intolerant, but can handle about 1/2 a cup of milk every few days without issue. Whey protein and aged cheeses give me no trouble at all. On the other hand, I gave a friend of mine a protein shake one day and he had to go to the hospital from the reaction. We had thought he was lactose intolerant, but it turned out it was the protein he was allergic to.
Anastas Dimitar Martin