Ds has a friend who has been eating at our house for 7 years and she is deathly allergic to dairy and is unable to eat beef because of the protiens. She has to be extremely careful about cross contamination as even the smallest hint of dairy can cause a reaction which would require her epi pen and a trip to the ER.
She must have some other issues other than milk. And yes cross contamination can be fatal. Like the above pp I had a very good friend
who's son was epi pen allergic to milk even laying his cheek in a drop of his little brothers formula caused a reaction. But could eat beef. However he did also have issues with other foods than came up a little later in life.
These allergies are horrible and I feel for anyone that has to deal with them.