Eli5: Why are we told to wash our hands for 20 seconds to kill all the bacteria etc, but not told anything similar for dishwashing? What makes dishwashing different, if anything?
In: Biology
Simply put, bacteria won’t stick to a non-porous surface and by using a detergent or soap you essentially smother your hands in a product of the soap called a surfactant that reduces the surface tension (that slick feeling) and creates a film-like barrier between your skin and the bacteria which allows the bacteria and germs to slide off your hands when you rinse the soap off.
Your hands are extremely porous and come into constant contact with exposed liquid transition points where the bacteria can transfer and thrive within your body such as rubbing your eyes, scratching inside your ears, biting your nails, picking your nose, cuts on your hands and fingers, etc.
The vast majority of dishware is non-porous and doesn’t have recesses or compostable organic material for the bacteria to stick to and grow. This is why food left on a plate will eventually mold, but they are islands of mold only bc they have a source of organic material to feed off of. Additionally, machine dishwashers also employ hot water, heat, and steam to sterilize the dishware, which would scold your skin and cause blistering. Harsher solvents are also used, such as jet dry using chemical agents to reduce hard-water spots and facilitates quicker evaporation. Or Finish detergent powder which is strong enough to cause considerable joint pain and swelling if exposed to repeatedly for lengthy periods of time, but it is better at dissolving organic material without the need for direct scrubbing pressure and is highly soluble in water.
However, if you mean more hand-washing dishes, much of the same applies. You use a softer solvent, such as Dawn, so the skin on your hands doesn’t dry out and crack, and the water is a bit cooler so you’re not boiling yourself alive, but you work harder to remove the stuck on debris.
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