The typical human body contains about 100 trillion cells. Only 10 trillion or so are technically part of the body. The other 90 trillion are hitchhikers. A particularly cozy home for bacteria is provided by the intestinal tract, where most of the foreign residents do far more good than harm by aiding digestion and absorbing toxins.
In an age when almost every household and personal care product brags “kills germs!” it is worth noting that killing germs is not always a good idea. The anti-bacterials in our soaps and cleaning products overwhelmingly kill benign or harmless bugs while helping to breed chemical resistance in dangerous ones. What is more, many scientists blame our highly sanitized modern Western lifestyle for the ever growing numbers of children’s allergic disorders, which have doubled in the past ten years alone, and for the steady rise in asthma rates in the past thirty years. Christopher Lowry, professor of physiology ay the University of Colorado, remarks, “The hygiene hypothesis is widely accepted among immunologists. It suggests that we have less exposure to certain organisms in the soil and water than we used to.” Lowry believes this may not only make us wheeze but may increase depression and anxiety as well, since these are exacerbated by immune response inflammations. It seems if we don’t give our immune systems something useful to do, they will find something inappropriate to do. Joel Weinstock, chief of gastroenterology at Tufts University, even suggests that “deworming the population… is one factor that led to the rise in immunological diseases.” (He probably is right, but I plan to skip the worms and take my chances.)
No one is suggesting we ignore basic hygiene. There are, as we know, potentially lethal diseases that can be spread by improper sewage disposal or by unsafe drinking water. Washing your hands is still the best way to reduce the number of colds and infections you catch. As with anything, however, there can be too much of a good thing. Whether we like it or not, we are one tiny part of a biological world full of organic grime and microbes. We do ourselves no good by being overly fussy about it. As Ella Gudwin, director of strategic initiatives at AmeriCares, so charmingly puts it, "The whole world is covered in a small film of fecal matter. Just get used to it."