We are seeing what many scientists call the “Allergy Epidemic”, a two to three fold increase in allergic disease and asthma in the late 20th century.
An interesting article was recently published in the New York Times on November 9th explaining this phenomenon. The highest population of allergy sufferers are in developed, Western countries. The article shows that people who grow up on farms have less allergies. It is explained that high exposure to a lot of bacteria (i.e. manure) at a young age trains your immune system to fight infections and therefore not over respond to harmless stimuli (allergies).
It is hard to make any life changes to develop less allergies based on this article (unless you want to move to a farm), but one should not use or give their children frequent antibiotics unless its absolutely necessary and after consulting with their doctors, as other studies have shown that this could “shift” ones immune system to developing allergies.