If you've followed science news at any point over the last fifteen years or so, you've probably heard of the hygiene hypothesis. First proposed by researcher David Strachan in 1989, the hygiene hypothesis is one attempt to explain rising rates of allergies in North America and Western Europe and higher rates of allergies among children raised in suburbs than on farms, and in smaller families as opposed to larger ones. It proposes that children in Western societies decreased exposure to germs and other disease-causing substances due to some characteristics of modern Western lifestyles has affected the human immune system's opportunity to develop standard immune responses, and that this lack of opportunity has somehow primed human immune systems to develop allergies.
But while the hygiene hypothesis is one of the more widely studied, and widely accepted, potential reasons for the recent rapid increase in food allergies in Western countries, the "solution," inasmuch as there is one, almost certainly isn't quite as simple as packing up and moving to a farm and rolling around in the nearest mud pond. First of all, while the hygiene hypothesis may explain the "what" of rising allergy rates (and even on that there's debate), the "why" is still undetermined. Assuming the hygiene hypothesis is true, recent research has speculated that lack of helpful bacteria in the small intestines, exposure to infectious diseases, or even certain parasites may be the root cause. Thus far, none of these have been proven as the method by which the hygiene hypothesis works.
Perhaps more importantly, good hygiene works for preventing some severe infectious diseases. Keeping food outside of temperature "danger zones" can help prevent colonization by bacteria that can cause foodborne illnesses like E. Coli and Salmonella. The CDC considers hands the most common disease-transmission vector, and hand washing the best way, to prevent potentially lethal illnesses like avian influenza H5N1. We don't know exactly how the hygiene hypothesis works, or which organisms the immune system may need to be exposed to early in life in order to prevent the immune system from developing allergies, but we do know that practicing good hygiene saves lives and prevents disease.
While the hygiene hypothesis isn't, at present, a basis for behavior changes to prevent allergies, it's mentioned frequently enough in news reports that it's worth knowing about. Learn more about the hygiene hypothesis here: