I was told that it was inadvisable to use extremely hot water to wash dishes with dish detergent, because that might change the chemical composition of the dish detergent.
That had me wondering: At what temperature of water does detergent and soap change its nature? Probably a temperature too high for human skin to handle anyway? In other words, you can wash your hands with hot water and soap and it wouldn’t change the chemical nature of the soap into something else. You’d probably still hurt your skin of course, but the soap wouldn’t become something other than soap…?
If we take it that the Dish detergent is Sodium Laureth sulfate, then that is stable up to boiling at 650 C (approx).
Now if you were paying for laundry detergent that contains enzymes, and then added it to water that was scalding hot, eg above 50 C, then those enzymes may be destroyed by the high temperature. The enzymes are biological agents,in that they are made by bacteria, and are made OF amino acids… the amino acids are sensitive to being cooked.
So seems the story you got was crossed. the temperature limit is for laundry detergents, but only those that contain enzymes.