Quote Originally Posted by Theseus View Post
I can't find the article now, but I read a couple of years ago how the rise in peanut allergies might be related to the decrease in breast feeding. Not sure how true it is, but it certainly makes sense to me.
I suspect - and I'm not that kind of doctor - that there is no one single cause for the spike in allergies. All of the reasons frequently suggested seem plausible to me:

Reduced rates of breastfeeding: human physiology evolved for a heck of a long time on the understanding that we would start our lives with human milk as our primary food source. From it we gain not only nutritional value, but also antibodies, etc. It just makes sense to me that removing this from the equation could well have an effect on the development of one's immune system (amongst other things)

Overzealous hygeine: as we grow and our bodies encounter the things in the world around us, we learn how to deal with the 'stuff' that we encounter. As a result our immune systems learn and develop. Remove the little infections, etc., and you will surely compromise the body's ability to identify and deal with real threats

Environmental factors: we are all surrounded by stuff that simply didn't exist all that long ago. Phthlates and BPA are two examples we've heard a lot about recently. As Trimmy72 said, we are all exposed to all kinds of things with absolutely unknown long-term and cumulative effects. Could these effects include increased allergies? Again I can't say for sure, but I wouldn't bet against it.

I suspect that it is a result of a combination of these and other factors, and not a simple single cause.