Our clean living is killing us -- more and more, science is finding that our war against minor ailments, is leaving us defenseless against our own immune systems. Studies in rats have shown that those that live in the wild -- sewers, farms, etc. -- have immune systems that are well tuned to fight more troubling infections, while ignoring minor irritants. Lab rats on the other hand, accustomed to living the clean life, have immune systems that go wild when they encounter minor infections. This view, that our clean living is killing us, subscribes to the hygiene theory, which states that exposure to allergens in the environment early in life, serves to boost our immune system later -- an assertion that has credence when allergy rates of city and rural dwellers are compared. So what do you do? Live a little dirty. Get a pet or two; houseplants or two; and don't be afraid of going outside -- especially for the little ones. Related reading : Allergy, Parasites, and the Hygiene H...