I desperately hope this is the case, but a quick google couldn't find a link. Do you happen to have a citation that you'd recommend? I say this as someone who is a bit paranoid about hand cleanliness _and_ is very tired of cracked skin.
Beyond the citation though, it makes logical sense. The mechanism for sanitation is that the soap itself destroys the bacteria. This mechanism works regardless of temperature. Cold water + Soap should be just fine as long as your hands are otherwise visibly clean.
In the food industry, we were required to use high temperature water. This was presumably to remove actual surface contaminants (dirt, grease, other food contaminants) rather than for actual sanitation. That's why you might still see guidelines for using hotter water temperatures.
I've always been taught it's the latter. Soaping your hands, and not rinsing will not sanitize them, you'll just end up with dirty, soapy hands.
Cdc agrees:
https://www.cdc.gov/handwashing/faqs.html
> Is it better to use warm water or cold water?
> Use your preferred water temperature – cold or warm – to wash your hands. Warm and cold water remove the same number of germs from your hands. The water helps create soap lather that removes germs from your skin when you wash your hands. Water itself does not usually kill germs; to kill germs, water would need to be hot enough to scald your hands.
Soap helps break down/encapsulate/dissolve oils/fat that aren't readily soluble in just water.
Especially once lipids get involved (almost all hydrophobic), especially in combination with other types of substances like oil soaked dirt or dead skin (like what you get on a doorknob at the micro level), it just doesn’t work the same way on the same timescales with colder temps - it fundamentally can’t, chemistry doesn’t work that way. [https://www.chemguide.co.uk/physical/basicrates/temperature....]
If you want the same speed of reaction - aka same amount of oil converted to a not oil - with lower temps (and hence lower molecular velocities and less Brownian motion) you need more reactive chemicals and more aggressive physical action to get compound A in contact with compound B enough to have the reaction you need. It’s as true for soap as it is for anything else.
And this all of course has a giant * on it, since above a certain point the energy in the system causes parts of it to disassociate or form unwanted side reactions, so there is a limit where it ‘blows apart’, ‘crashes’, or ‘can’t stick’ to extend the analogy. I can’t think of any soap that would have that problem at temps within human ‘not going to immediately get 3rd degree burns’ ranges.
I'll be really interested if i can avoid warm water.