My oldest was born in 1999 and the hospital sent us home with a list of foods that we shouldn't introduce to our children until they were three years old. I remember this because both peanut butter and honey were on the list, and one of my favorite foods is peanut butter and honey sandwiches. I have six kids, and I got in trouble quite a bit over the years because I gave my infants bits of my sandwiches.
What can I say, they liked them...
It's a bit funny to me that I was actually right about that particular call. Most of the times that my wife and I disagreed about something I was definitely the one that was wrong.
Most new parents don't know anything about raising children, and even the worst parents are pretty motivated to do a good job. New mothers, in particular, are desperate for solid advice on what to do with their new child. My wife isn't keen on reading the instructions for any purchase that she makes ever. No matter what it is that she buys I am the one that has to read the instructions and teach her how the thing works. That was true with our children as well. However, she made me read every pamphlet that the hospital sent home with us when our babies were born dozens of times over. If she thought I was interpreting them incorrectly she would wait a bit, cross examine me again, and force me to show references. If one of those pamphlets would have said that the best way to insure that the child grew up healthy and strong would be to murder the father and sprinkle his blood over the baby by the light of a full moon then I probably wouldn't have survived the first full moon after my daughter was born.
Someone in the medical community decided that the best way to protect children was to keep them away from certain allergens, and they put that opinion into the pamphlets that get given out to new parents. I am sure that the people that came up with that strategy meant well, but in they theory was proven incorrect.