Until a doctor told me: get off the milk. See what happens and try to reintroduce it. I have now been milk free for three weeks. The rash is almost gone. You can still see the contures of the former rash. But it is nothing like it was a month ago. I still have hopes to be able to eat milk products now and then. But I am also painfully aware of that that might not be possible.
I am also more and more open for the message that milk is maybe not so beneficial as the formal verdict wants to portray it to be. Instead of strengthening bones, it might actually do the opposite. And a lot more. But I am still decolonizing my mind. Milk (and particularly cheese) is way to yummy to give up just like that. I need some time to digest my milk free lifestyle.
If you want to know more you can watch this youtube clip by the (paleo-inspired) medical doctor Mark Hyman. He gives a lot of insight to the subject:
Btw, I actually think that milk might be ok for most people, but that casein is problematic for those who have a digestive system out of balance (due to stress or other reasons). This is my personal speculation though.