Dr. Andy

Reflections on medicine and biology among other things

Wednesday, March 01, 2006

Eat dirt, prevent asthma!

Why have asthma and other allergic diseases gotten so much worse in the last 50 years? No one knows for sure. A leading hypothesis is called the “hygiene hypothesis,” which states that we are too clean. Initially the idea was that we got fewer infections than we used to before immunizations, antibiotics, antimicrobial soaps and gels, etc. However, studies haven’t been able to show, for example, that kids who get antibiotics earlier or more frequently are more likely to get allergic diseases than those that don’t

A new modification of the hypothesis suggests that it isn’t lack of exposure to microorganisms that cause infections that is the problems, but lack of exposure to harmless bacteria and fungi, particularly those that live in the ground. Studies clearly show that growing up on a farm is protective against allergies (as shown in the first graph) and that the more rural the environment the better.

One problem is that measuring the extent of urbanization is difficult. Now, 2 Finnish researchers writing in this month’s Journal of Allergy and Clinical Immunology have come up with a good proxy, use of asphalt. As this graph shows, the increase in asthma in Finland closely parallels use of asphalt.

So if you want to avoid asthma, allergies, etc. eat dirt.

UPDATE: added link to original article. Link to criticism of second graph as misleading.


At 12:48 AM, Blogger IML said...

my grandma told us that long ago. Children need to grow up playing in the garden with the great outdoor. Parents today are too paranoid about sterilizing everything.

At 2:16 PM, Blogger Bob said...

So that little bit of mildew in the bathroom isn't too much to worry about?

At 7:32 PM, Blogger Flea said...

I've heard some fairly cogent-sounding refutations of the hygeine hypothesis, but I can never remember them. So the story I tell parents is the standard version hygeine hypothesis story.

I usually cap it off with the observation that I'm not going back to live on a farm and I don't expect most of my 300 million neighbors to do so either!



At 11:32 PM, Blogger filmwidow said...

Brighams and Women's Hospital did a study that shows the hygiene theory doesn't work in all situations. Asthmatic mothers have children who are more likely to wheeze when exposed to cats.


Having grown up in rural Montana, there's no way I'm going back. I like urban life way too much.:)

At 12:37 AM, Blogger TC said...

Thank you, Dr. Andy. I'm going to stop cleaning this very instant.

At 2:38 PM, Blogger mrsgarageflower said...

If ever there was a text book case it's my in-laws. Mom, the nurse, learned everything below the waist is "contaminated" and all 3 kids grew up in a sterile home, no pets, no dirt and no outside. All 3 over weight with myriad of health problems including allergies and asthma (and diabetes, etc).

At 9:33 AM, Anonymous buy generic viagra said...

Interesting. It's a good information, specially if you posted a drawing which shows information in a simple way to understand everything about this allergic diseases. I think I already know that, because it's all about bacterias against medicine.

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