No, I think (God help me again) that environmental toxins, traffic exhaust, the whole living-in-America pollution thing is what's doing this to us.
The immune system gains strength as a child matures. Children who are susceptible to allergies benefit by delayed introduction to foods until their immune system is able to cope more effectively. Of course, very little can be done about the environmental pollutions that we all breathe and live in if we are in an area that's highly polluted.
Beyond this, there is also medical research that points to specific brain wiring that makes a person more allergy prone. While the basic structure of the brain is similar among humans, there are many, many variations. For example, gifted persons are more likely to have allergies than non-gifted folks. Giftedness is seen to be (partially) hereditary.
Correct me if I'm wrong, but doesn't the brain plays a major component in allergic reactions because it recognizes a particular substance as a threat, thus giving off histamines?
I think there is a lot that you can do to help prevent allergies, as has been discussed on this thread. And there is a lot that can not be helped such as genetics and living in a world that is more polluted than was 50+ some years ago. But I see the bottom line as being that because we are all unique and different individuals, our individual bodies have so many variations, even living under the best circumstances, eating the "right" foods, etc. is no guarantee that our children would be allergy free.