How cleanliness can kill

The hygiene hypothesis is that our immune system requires the presence of pathogens to grow and function properly. The thinkin is that dirt ‘n’ muck provides a kinda training ground on which the immune system “learns” it’s trade when we’re all youngsters.

So mothers who keep a-scrubbin and a-cleanin them germs away are actually doin’ more harm than good. Their littluns’ immune systems ain’t never gonna learn how to fight off invaders.

Alotta medical bods think the hygiene hypothesis makes sense. They say it’s cleanliness that causes asthma and other allergies, not dirt. And the evidence is growing to back ‘em up. But exactly how this balance between pathogens and our immune system works ain’t known.

Now Didier “See” Sornette at the Swiss Federal Institute of Technology in Zurich and a few buddies have built a mathematical model of the immune system based on this idea. Their assumption is that a balance exists between the immune system and the many pathogens that it comes across each day. (FYI our bodies are built outta 10^13 cells but house something like 10^14 bacteria.)

See Saw and his pals study two ways that this balance can change. The first is an external attack of pathogens such as a cholera epidemic or an infection following major surgery. Obviously that don’t do nobody no good.

But another type of change occurs when the immune system itself becomes weakened, perhaps by stress, lack of sleep or heavy boozin’. Then pathogens can spread even if the body ain’t exposed to an abnormal load.

See Saw’s work consists of exploring the topology of this mathematical model and findin’ areas of stability. The model predicts, for example, that a critically ill person can be made healthy by strengthening their immune system. Nothin’ strange about that. But it also predicts that ya can kill a critically ill person by reducing the load on their immune system. That’s when cleanliness kills.

So dirt might be even better than we thought. Not only does it train the immune system, but it can keep ya alive too. And if that’s the case, sterile hospitals could be as bad as dirty ones.

That’s gonna get people goin’ like a mongoose in a jockstrap. Ya’ll sit back and wait for the wailin’ and gnashin’ of teeth.

Ref: arxiv.org/abs/0710.3859 :Endogenous versus Exogenous Origins of Diseases

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