Sometimes amongst the bum jokes you’ll learn something really Quite Interesting on QI.
Last week I learnt that when washing hands, how clean you get them is not about the heat of the water, which can’t possibly be warm enough to kill off bacteria and escape without serious burns. Rather, it’s about how vigorously you wash them — that is, you’re getting the bacteria off your hands, rather than killing them.
There’s probably more to it than that — the Wikipedia article on hand washing notes that: warm, soapy water is more effective than cold, soapy water at removing the natural oils on your hands which hold soils and bacteria. Contrary to popular belief however, scientific studies have shown that using warm water has no effect on reducing the microbial load on hands.
Perhaps I’ll just stick to my current habit: soap and warm water.