Breadcrumbs, by which I mean tidbits of information that help me find my way, are coming thick and fast now that I've discovered podcasts. This morning I listened to Science Talk, a half-hour show from Scientific American, on the Hygiene Hypothesis. The title is "Can It Be Bad to Be Too Clean?"
The idea is that we can be too clean, too quick to wipe out microbes, and this change from earlier, dirtier environments has been so fast that the delicate balance of pathogens and our bodily responses has been affected. On the podcast Johns Hopkins researcher Kathleen Barnes mentioned two specific types of immune responses. One is geared toward microbes, and the other toward worms or parasites. It seems that when challenges to one are absent in early childhood, the other one gets out of whack. At least, this was my understanding. You can see the summary on this Scientific American webpage.
Here's an excerpt from www.hygienehypothesis.org :
Eliminating typhoid and cholera has saved millions of lives in the aggregate since sewers and clean drinking water were introduced in North American and Western Europe for instance. But in so doing we contributed to the rise of the modern diseases involving immune dysregulation, like Multiple Sclerosis, Crohn's, Ulcerative Colitis, Graves Disease, Hashimoto's Thyroiditis, Type I Diabetes, Asthma, Allergy, Coeliac Disease, and Sjogren's Syndrome.
I played in the dirt a lot as a kid in the suburbs of Indianapolis. I ate strawberries from the banks of the shallow drainage ditch behind our house, and built mud dams all the time. This was outer suburbia, one house away from working cornfields.
I happen to be completely free of allergies, although my mother had a severe life-threatening allergy to shrimp. By the way, I am diabetic Type 2. Mere anecdotal evidence, of course. Your mileage may vary.