People today are clean freaks. They are obsessive about washing and showering. When I was a kid growing up, you had a bath once a week. You washed your face and hands every day, or when they got dirty. Only those who worked at dirty jobs washed their entire bodies every day. In prior centuries people might go months without bathing. They wore their clothing until it got filthy, then gave it away to poorer people and bought new clothing. They used scents to cover up body odor. The human body has no need to be washed every day, or several times per day. That is a convention of our times -- our skin does very nicely on its own without being washed for weeks or even months.
To your point- a researcher in gastroenterology theorized inflammatory bowel diseases developed because the modern gut has "nothing to do". Back in the day when humans ate whatever they could the bowel was too busy digesting dirt and bugs and getting worms- stuff like that, to digest itself. This researcher then developed "helminthic therapy", literally worm therapy that appears to activate an immunologic cascade that helps to restore the human gut/immune system biome.
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