"... The prevailing theory is known as the Hygiene Hypothesis. Simply put: we’ve become victims of our own compulsion for cleanliness. “In the past 20 or 30 years, we’ve certainly been living more cleanly. Our housing has changed, we take antibiotics, we have vaccinations. So our immune system, which has less infection to fight than it has in the past, has become dysregulated, and has begun to react and become hypersensitive to things in the environment that are harmless,” says Dr. Susan Waserman, an allergist and clinical immunologist at McMaster University in Hamilton, Ont. “Why should anyone become allergic to something like a peanut or ragweed? It doesn’t really make sense.” The hypothesis is supported by the fact that the entire western world, including the United States and Europe, has experienced the same allergy trend. One well-known study compared relatively clean West Germany with more polluted East Germany and found far lower levels of allergies in the East (although, since unification and the westernization of the East, the levels have risen sharply)... "