One suggested explanation for the increased incidence of food and other allergy is the hygiene hypothesis.
This hypothesis proposes that kids who grow up in more sanitary environments are at increased risk for developing allergies. The heightened risk is owed to getting less exposure to microorganisms that stimulate and strengthen the immune system.
Although the hygiene hypothesis is still far from fact, there are plenty of scientific thoughts and data behind it:
Germs and the Immune System
Beside the research and reports supporting the hygiene hypothesis, scientists also have a reasonable explanation for how highly sanitary conditions might alter the behavior of our immune system.
Our body is designed with two immune system pathways. The Th1 pathway uses small IgG antibodies to fight bacterial pathogens. The Th2 pathway releases the larger, and more inflammatory IgE antibodies to destroy unwanted parasites. People with allergies have immune systems that are biased toward the Th2 response.
It’s possible that a lack of exposure to microorganisms early in life disrupts the balanced development of the Th1 and Th2 pathways. This unbalance might allow excessive Th2 (IgE) reactions to what should be harmless proteins, such as those in eggs and nuts.
Though unsanitary living conditions come with their own set of nasty health concerns, a high rate of allergy isn’t one of them. However, if the hygiene hypothesis proves to be valid, there is no point in berating ourselves for becoming increasingly sanitary. We can instead acknowledge that even good things sometimes have unforeseen consequences—and maybe invite a little more dirt back into our lives.