As someone who flirts with the hospitality industry, I actually find handwashing morbidly fascinating. The CDC has officially changed its stance on the temperature you should use for washing, saying cold water is similarly effective, while being more carbon friendly. The study that underlies this change is called “Handwashing Water Temperature Effects on the Reduction of Resident and Transient (Serratia marcescens) Flora when using Bland Soap,” published in 2001 by Barry Michaels et al. The study seemed flawed to me, so I asked someone I respect who is a practicing American MD with two specialties, internal medicine and interventional radiology. He knows about washing hands.
Four whole people were sampled! Dumb bad or good luck could bolster or refute this “study.” Having said this, I could believe it. But this did not account for the water temperature effects on soap, just bacteria. Soap work based on micelles [an aggregate of molecules in a colloidal solution]. And micelles have to contact a hydrophobic and hydrophilic item to work. Hard and soft water differences with soap and its temperature come to mind. I am a bottom line physiology thinker here: When molecules move faster, there is more effect from the movement. Why does the body innately increase its temperature when infected? And why serratia [a bacteria responsible for hospital infections] of all choices!?
I am going to stick with hot water hand washing, for now.