It's beasue milk protein could be passed into breast milk. 小龍女她媽
My doctor told me when we found my baby has milk allergy.
You should try Nutramigen as I suggested yesterday. If this still doesn't work, please try Elecare.
Here is the manufacture website for Nutramigen. You may get liquid form from here. It's a safe site since I have been ordering from here for more than one year. I didn't use Elecare. But it's a special formula for those babies who has severe allergy. it's very expensive.
Good luck