Very interesting. While the theory that most peanut allergy is caused by no exposure in infancy is well supported by the evidence, seems like it’s definitely not the entire story, given your experience — after all, you could hardly have a lot of exposure in children to peanuts earlier than 5 months! I don’t think we were feeding our kids solid foods at 5 months yet at all, so definitely they had no peanut exposure yet, but nevertheless they don’t suffer from allergies. The evidence you are pointing to about disparate rates of allergy for children growing up in different places is also very interesting. Sounds like there just is something in the air, or dirt, or daily practices, or whatever else it is, that causes those allergic immune reactions at elevated rates in western nations.