On a business trip to Boston, I met up with a college classmate I had not seen in 20 years. I told him about the severe pollen allergy I developed after 5 years of living in the U.S. I blamed it on fertilizers and pesticides in the food chain, and on kapha-inducing dairy products. Eating organically grown foods and avoiding dairy helped somewhat but my condition is far from cured. Oddly enough, for the first 23 years of my life, in India, I suffered no allergies whatsoever.

His wife, a microbiologist, asked if I had heard of the Hygiene Hypothesis. She explained it thus: exposure to germs develops the body’s immunity and prevents allergic reactions to common but harmless substances such as pollen.

Evidence to support the hypothesis is mounting. In the last decade, German researcher Erika Von Mutius found that East German children who grew up on farms and handled farm animals regularly had a lower incidence of allergy and asthma than West German children who grew up in cleaner urban environments.

In 2000, a study of children in Gabon found that the presence of helminth worms in their bodies allowed them to produce an anti-inflammatory substance IL-10 that suppresses allergic reactions. Asthma patients are known to be deficient in this substance.

This month, an article in the journal Science (19 April 2002) confirms that finding. It reports that the presence of parasitic worms in the body has been associated with a lower incidence of allergic disorders.

Damn. Who knew dirt and bugs could be good for you. We all know the connection between unsanitary conditions, harmful microbes, and disease. Now we are finding out that there can be such a thing as an overly sanitary lifestyle, and that the utter absence of microbes can be harmful in its own way.
This hypothesis is counter-intuitive. You expect a cleaner, more germ-free environment to produce a healthier body. Yet, the basic principle of immunization is that exposure to microbes develops immunity, not an antiseptic environment.

I would love to cure my allergy, but I can’t bring myself to do what a Japanese parasitologist did. Koichiro Fujita of the Tokyo Medical and Dental University swallowed three tapeworms who now call his gut their home. As you recoil in horror at the thought, dwell also on this: his hay fever is gone for good.

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