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The hygiene hypothesis
Society has come a long way in battling deadly diseases and plagues that once had the potential to devastate entire countries. However, with the emergence of better sanitation, antibiotics, and vaccinations, a new problem is arising. An increasing obsession with cleanliness and sterility may be having the opposite effect -- making children more susceptible to illnesses and allergies.
There are millions of bacteria, viruses, harmless parasites, and microbes that act as "exercise" to the immune system to help it learn how to fight off diseases and infections. A January 2009 article in the New York Times explored this topic and the instinctive behaviors babies exhibit when they eat dirt, suggesting this act has helped us evolve and survive as a species. Ingesting the parasites, bacteria, and worms found in dirt reportedly helps children develop appropriate immune regulatory circuits.
However, more and more children are now being raised in an ultra clean environment, and many scientists are supporting the notion of the "hygiene hypothesis." This is the idea that antibacterial agents commonly used in soaps and household cleaners are also killing off more than one-third of the good bacteria that are essential in bolstering immune systems.
According to the National Heart, Lung, and Blood Institute (NHLBI), some scientists believe that this has caused the occurrence of asthma and allergies to increase noticeably in children over the past three decades. Nearly 5 million children under the age of 18 now suffer from this illness. Estimates from the NHLBI show this is a 75% increase overall since 1980, and a 74% increase in children between the ages of 5 and 14.