It's worse in cities, where "nearly 9.8 percent of kids had food allergies." In rural America "only 6.2 percent did":
The so-called hygiene hypothesis holds that exposure to "dirt" (which includes bacteria, viruses and worms) forces young children's bodies to develop a healthy immune system. It follows that if you're not exposed to all the nastiness that the natural environment has to offer—which you might not be if you grew up in a concrete jungle and have parents who douse you in Purell—you'll be more likely to have a weak immune system that does things like have allergic reactions.
J. Bryan Lowder cautions:
The main problem is that researchers rely on responses to surveys, which, of course, are subject to the biases of self-reporting and memory. And parents who take the time to respond to such a survey are likely already invested in the subject emotionally, further clouding their answers.
The Dish 