Do not test for allergies at home unless advised by a doctor.
We tested our daughter with milk this weekend. I made an icing and put in on cookie. She reacted to it with hives. But it was a milder case than in the past. We didn't even give her Benadryl.
I have been feeding her more and more dishes with milk cooked in them and she is tolerated them just fine. Ah, no more making two of everything. Although I still will if I think something might have too much "milk" in it.
It's a really good feeling to see her slowly being able to eat more.
A little update
3 years ago