Two pull quotes from this National Geographic article by Brian Clark Howard
Carrico said, “It’s certainly true that heat kills bacteria, but if you were going to use hot water to kill them it would have to be way too hot for you to tolerate.”
In fact, she noted that hot water can often have an adverse effect on hygiene. “Warmer water can irritate the skin and affect the protective layer on the outside, which can cause it to be less resistant to bacteria,” said Carrico.
I always knew the climate change aspects of using a lot of hot water (especially waiting for it to heat up), but never really thought about the rest.
I’m still going to take showers in warmer water though.