I know this may be controversial, but my mother did not breast feed, she used formula, which probably included dairy, who knows, maybe that is why me and my siblings have no dairy allergies.
I remember reading that a trend toward sanitizing and adding anti-bacterial ingredients to plastic toys and playground equipment was ill advised as it short-changed kids growing up on developing a robust immune system. Made sense.
Dairy allergies can develop after breast feeding time. Some children do poorly on cow milk based formula. Our children are adopted, and so had a mix of breast milkand formula. The two who are black have dairy sensitivity (common among black and oriental people), oneof them severely.