DS is allergic to dairy & soy. 40% of babies that react to cows milk protein will have soy problems too as the proteins are similar. There is some info from our gastro pead on it.
kellymom has some good info on BF & allergies and time frames. I was told to eat everything else as normal and see if he reacted. DS was diagnosed at 6 weeks and I'm still BFing at 18 months 