Why is water and soap better than hand sanitizer?
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I’m not sure exactly how far down the rabbit hole I should go, so I’ll just go all the way and you can skip whatever you already know. Oil and water don’t mix. That is, you can’t dissolve one in the other. Water is a polar molecule, which means the electrons are concentrated slightly more on one side of the molecule than the other. Just like a magnet has North and South magnetic poles, the water molecule has positive and negative electric “poles” so we call it polar. Polar solvents can dissolve polar solutes. Oil, however, is nonpolar and won’t dissolve in water.
Hand sanitizer uses either ethanol or isopropanol as it’s bacteria-killing agent most commonly. Both are polar molecules which dissolve in water. If you have oil or grease on your hands, it will not mix with the hand sanitizer. Even if it did, you do not wash away the grime, you put it on your hands, rub it around a bit, then let it evaporate.
Soap is an interesting molecule. It is a bit longer with one end that looks and acts very similar to a polar molecule, and the other end looks and acts like a non-polar molecule. I think, logically that means it is technically polar overall, but the tail is far enough from the head that the polarity doesn’t affect interactions down there. This means it can bind well with the oil and grease on your hand, but also with the water used to wash it away. Not all soap is antibacterial, but even if it isn’t, they will mostly get washed away too. Plus, the cell wall of bacteria is also fatty like oil. The soap can bind with it and actually molecularly disassemble the bacteria. Sort of, indirectly killing it. I don’t know how likely this is and how much of an effect it plays overall, but I have heard that it is possible before, and it makes sense to me.
One other thing to consider, some people are scared of creating super bugs that will be resistant to antibiotics. Anti-bacterial hand soap does use antibiotics. Whereas alcohol is already lethal to bacteria, so no additives needed. And I’m quite certain they can’t grow immune to alcohol… At least not without DRASTIC changes to their entire structure.
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