Comment by lawtguy | Hacker News Reader

Comment by lawtguy | Hacker News Reader

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I find the "Old Friends" hypothesis a good answer for why hygiene causes allergies: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1774411/

The basic idea is that the human immune system has co-evolved with a number of immune suppressing parasites. Hygiene has greatly reduced the number of these parasites we're exposed to and without them the human immune system is too reactive. That extra reactivity results in our immune system attacking proteins that are harmless, like pollen or peanuts.

So hygiene is definitely extending human lifespans by preventing us from getting deadly bacterial and viral diseases. But it may indirectly be causing auto-immune diseases. The good news is it's not all that hard to introduce safe parasites back into our bodies: http://en.wikipedia.org/wiki/Helminthic_therapy

It's like Wolverine's healing factor that went crazy once Magneto stripped the adamantium off his bones.

Interesting. Could that be why people with overprotective mothers (often "indoor kids", nerds) tend to have allergies? As infants their cribs and highchairs were meticulously kept clean and sterile with disinfectant wipes.

The last time I've seen information and discussion about this, I've considered the viability of humans creating an artificial parasite to replace the parasites we are missing right now.

Cool link on the Helminthic therapy! I've never heard of it before.

It's a pretty cool idea. Although it's a tad simplistic way to consider the immune system, our bodies mount two types of responses: Th1 and Th2. Th1 favors our immune cells directly killing our own cells and baddies. Th2 favors our immune cells producing lots of antibodies which then tag baddies for destruction.

In Crohn's disease, our bodies, for whatever reason, seem to be skewed towards producing a really unnecessary Th1 response in the gut which causes our bodies to self-destruct the GI tract. By giving hookworms to a patient, the hope is that the needed worm-killing Th2 response (worms are too big for really an effective Th1 response and need to be coated in antibodies and essentially repeatedly nuked with cytotoxic chemicals) will shift the balance in the patient's gut from Th1 towards Th2, thus eliminating their Crohn's manifestations and symptoms. Really cool idea.

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