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I'll take a stab at this - I'm an infectious disease epidemiologist that works on hospital infections mostly.

The thing with anti-bacterial soaps is not that the use of the soap is bad. The problem is the anti-bacterial part. It puts amounts of a broad spectrum antibiotic into the environment (be it your hands, your countertop, or the water system) in concentrations that aren't enough to do much, but are enough to put a little bit of selective pressure on the organisms and promote resistance.

It's also not particularly effective - soap and water, through a combination of both mechanical action and how soap disrupts cell membranes, works swimmingly. So there's a cost, and no benefit.

The answer to 'why isn't there a resistance to soap' is that soap, as a chemical, is absurd overkill. It's hellish on lipids of all sorts (tough on grease...and lipid cell membranes), and there's nothing to evolve a resistance to. Not expressing a particular protein, or expressing an enzyme that does a number on an antibiotic compound is effective - to evolve a resistance to soap, you'd somehow have to develop an entirely new type of compound to build cell membranes out of.

And while evolution is rather magnificent, that's asking a little much.




Bacteria evolving to secrete a soap-resistant compound doesn't sound far-fetched at all. Such compounds clearly exist already (e.g. pigments that don't wash off).

Thinking about this more, I suspect there already has been some selection in this direction, but that it has little to no public health impact, as this defense is not useful in places where infections are typically a problem. Indeed, our body is teeming with bacteria (mainly in the guy) that are in fact beneficial, and they've presumably managed some resistance to shear stress and extreme chemical environments (e.g. high acid).


How do you feel about Triclosan in toothpaste?

I dated a heatlh care professional for a while who was pretty adament that it was causing detrimental effects in the same manner as antibacterial soap.


That one is...a little trickier. There is some evidence that it works for controlling bacterial growth leading to gingivitis - suggesting there may be some utility for it. But its ubiquity in consumer products makes me a little skittish.

So I don't know if I'd want it gone from toothpaste, but I'd like to see it gone from the many products where its useless or nearly useless, but included so someone can put 'Antibacterial' on the label.

Like soap. Soap is already antibacterial.




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