Are we too clean?

Source: Adapted from Allergy & Asthma Relief, Reader’s Digest

Although no one knows why the incidence of allergies and asthma is skyrocketing, a leading theory holds that the Western world is simply too clean. Some researchers call this the hygiene theory. One researcher, Marc E. Rothenberg, M.D., Ph.D., section chief of allergy and clinical immunology at Children’s Hospital Medical Center of Cincinnati, calls it the delinquency theory, as in the immune system has so little to do that it turns into a kind of physiological ‘juvenile delinquent,’ just itching to get into trouble. It’s a much-studied theory: Since 1997, scientists have published more than 6,000 research reports examining the apparent links between civilized living and allergies and asthma.

The problem stems from the tremendous advances we’ve made in the past 50 years in combating infectious diseases, parasites, and other pathogens. With vaccines eliminating many previously common childhood diseases, antibiotics vanquishing others, and the penchant for cleanliness (just think about the tremendous explosion in sales of antibacterial wipes, soaps, and lotions), a germ doesn’t stand a chance.

This means the immune system is left sitting around, twiddling its virtual thumbs. Its entire function is to recognize the difference between ‘self’ and foreign bodies. Self is fine, and some foreign bodies are bad (think about HIV and E. coli). Yet many foreign bodies you come in contact with (such as the hundreds of food proteins you eat and the thousands of molecules you breathe in daily) are also fine. The immune system has to learn at an early age how to tell the good foreign bodies from the bad, just as a toddler has to learn what ‘hot’ means. One way it does this is through encounters with endotoxins, molecules that occur naturally in every bacterium’s outer envelope and are released into the environment any time bacteria die.

The fewer endotoxins your immune system encounters in childhood, the less likely it will learn that important difference. Instead, it may just start attacking all foreign bodies’as well as your own body. The result: diseases ranging from allergies and asthma to autoimmune conditions such as multiple sclerosis and rheumatoid arthritis.

Some evidence supporting this theory can be found in the disparate rates of allergy and asthma within a country. Studies in both Europe and the United States show that people living in rural and farm homes had far less atopy (genetic risk of allergies) and asthma, even though they had much higher exposure to endotoxins from living near animals. For instance, a study in Basel, Switzerland, showed that children of part-time farmers had a 76 percent higher risk of hay fever and other allergies than those of full-time farmers, suggesting that greater exposure to the farm environment can be more protective. Another study of asthma prevalence in children living on the Pacific atolls of Tokelau and in Tokelauan children living in New Zealand, a more modern environment, found that just 11 percent of the children living on the atolls had asthma, compared with 25 percent of Tokelauan children in New Zealand.

The fact that a spate of recent studies shows that children who have pets when they’re young are less likely to develop allergies when they’re older also lends credence to the delinquency theory.

Obviously, this doesn’t mean you should send your children out to the woods to fend for themselves, but maybe you can relax the hypervigilance many parents have and consider getting them a dog. The bottom line: A little dirt won’t kill ’em’and it may even help.

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