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Comment by chimeracoder | Hacker News Reader

> Hand sanitisers in offices etc. should be outlawed. There's simply no reason for their existence and using them probably weakens your immune system anyway. They are useful for situations like camping but that is all.

That, or we could just make sure we use sanitizers that have high concentrations of alcohol in these settings.

The bacteria referred to here require lower concentrations of alcohol to survive. They're not able to survive 100% alcohol (or close to 100%), and it's very unlikely that they could evolve to tolerate alcohol levels that high. The reason we don't commonly use high concentrations of alcohol is that it's more irritating to the skin (for the same reason that it kills bacteria). But in settings where killing bacteria is necessary, dehydrating the skin is an acceptable tradeoff.

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> They're not able to survive 100% alcohol (or close to 100%)

IIRC, there's something of a peak in the effectiveness curve below the close-to 100% [1] point for ethanol, having something to do with too high a concentration not actually penetrating cell membranes fast enough when there isn't enough water in solution already. It's been a while since I read up on it. The papers are out there, for the curious.

That said, I also recall the European standard of 85% (w/w?) being far better as a disinfectant, as supported by the evidence, than the US minimum of 62% w/w (or 70% v/v). Perhaps instead of a ban, merely increasing the minimum percentage to something that doesn't encourage resistance would be enough.

[1] 96.5% or thereabouts is the highest distillation concentration, above which it would be hygroscopic and come down to that if left open to air.

Thanks, that makes me feel better about buying hand sanitizer and adding 99% rubbing alcohol once it’s half gone because i’m cheap :)

That was actually another detail I discovere, although with much less data behind it, that mixtures of ethanol and isopropanol [1] could be more effective than just one alone.

Mixing the two works well for liquid formulations, where the dispenser is a fine mist sprayer, but I'd be concerned that anything gelled or with additives for a foaming dispenser might not mix evenly enough.

[1] The usual alcohol in "rubbing alcohol" and, of course, for the previously-mentioned reason, ethanol is excluded if it's 99%

"But in settings where killing bacteria is necessary, dehydrating the skin is an acceptable tradeoff." Only if doesn't hurt hand hygiene compliance.

Alcohol sanitizer dispensers could also have a separate moisturizer dispenser.

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