Ok, this is my own personal theory. I have no research to back this up....

I don't think it is exposure to peanuts themselves that initially cause the allergy, but to something that is very similar to peanuts, like a chemical or a virus or bacteria that has a protein on it that is similar to peanuts. After all, that is theory behind how some auto-immune disorders, including diabetes, are caused. If it was just to the nut then why are peanut allergies in african tribes where peanuts are a staple part of the diet, rare? It might explain the rise in allergies since our diet became very processed.

Now for my rant....

We haven't changed very much since the middle ages when mothers were blamed for everything that went wrong during pregnancy (including giving birth to girls!) Except then it was blamed on bad spirits, thoughts, and imbalance of humours. Now it is because our diets are wrong. If your child is obese, it's your fault. If your child, grandchildren, great grandchildren have high blood pressure, it's your fault. If they have diabetes, your fault again. And allergies??? Absolutely your fault. I think we have to realise, as a society, that some things we just can't control, and nature controls everything eventually.