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
Part of it involved how porous a surface is. Dish ware usually isn’t very. Dish soap has two factors that make it helpful for cleaning. One of those is the fact it’s a surfactant, it slips into pores and creates a slippery environment. The other is the fact that it’s amphipathic because it’s polar and non-polar, this means it had properties that are hydrophobic (water hating) and hydrophilic (water loving). This property allows soap to act as a bonding bridge between water and lipids/oils. (It gives the “grease fighting” characteristic) This makes it effective against phospholipids. The other aspect has to do with moisture content. Usually, dish ware in a dishwasher goes through detergent washes and rinses that reach high temperatures. Some dishwashers also incorporate steam or heating elements to dry and sanitize the dishes. Hand washed dishes typically are given time to air dry before being stored. This dry environment makes it increasingly difficult for bacteria and viruses to thrive over longer periods of time.
Your hands on the other hand are extremely porous, so the act of rubbing your hands help drive the surfactant into the pores. You must also cover your hands with suds. Proper hand washing technique is as important as time taken. You can run your hands under a faucet but if you don’t properly scrub your hands, viruses and bacteria may persist. Surgeons use specialized soap, hand scrubs, temperature controlled water, and longer scrub times, as well as more stringent scrub measures to ensure their hands are as free of contaminants as possible, and then they’re followed by a glove.
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