How soap works

Cropped shot of an unrecognizable man washing his hands in the kitchen sink at home

We are told that washing with soap and water is an essential part of hygiene practices, killing microbes. We have seen many videos in the past few years about the technique, how long and how thoroughly to wash our hands, often accompanied by catchy tunes. Few of us understand the fundamental science of how soap works.
Soap and related products have a key function, one part of the molecule is able to bind to water and the other part to lipids (fats and oils). The outer shell of many microbes is made up of a lipid layer. The soap is able to break this open and make the contents spill out, rendering it harmless. The soap molecules surround the remains of the microbe, trapping it. The water-loving part of the soap molecule binds to the water running over your hands to move the contents away.
There are microbes that don’t have this fatty outer layer. Good handwashing protocols encourage you to scrub and this mechanical action lifts the microbes off your skin.
Alcohol-based hand-sanitiser (60% +) is more convenient in many circumstances and has a similar effect. Application of hand- sanitiser also requires you to use the mechanical scrubbing as you do with soap.

abs Lactobacillus Bulgaricus Bacteria – 3d rendered microbiology image. Medical research, health-care concept.

Hand hygiene is known to irritate your skin if you have to do it a lot as it stips the natural oils on your skin. I have worked in hospital settings and know this well. Caring for your skin after handwashing or disinfecting your hands with moisturiser is recommended.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8094276/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2446461/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8375726/