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I was recently told that I should use hot water to wash my hands rather than using cold water because the hot water will kill germs better. The person who told me this isn't a very reliable source, so I'm not sure if I should believe them or not. It does seem like it makes sense, though.

Does washing your hands with hot water kill germs better than washing them with cold water?

  • It might not kill germs with such low temperature and short amount of time, but it should make you feel a bit more comfortable especially in cold weather though. – xji Apr 7 '17 at 11:52
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Surprisingly, no. Hot water does kill bacteria, but what's comfortable for your hands is also pretty comfortable for bacteria. Most pathogens start to die off around 60°C to 70°C (140°F to 158°F)1, but water from the "hot" tap in a sink is typically below that (40° to 55°C or 104° to 131°F)2. In order to kill bacteria, the water would have to be way too hot for you to tolerate.

According to National Geographic, in Washing Hands in Hot Water Wastes Energy:

Carrico said that after a review of the scientific literature, her team found "no evidence that using hot water that a person could stand would have any benefit in killing bacteria." Even water as cold as 40°F (4.4°C) appeared to reduce bacteria as well as hotter water, if hands were scrubbed, rinsed, and dried properly.

This agrees with the World Health Organization's conclusion3:

Water temperature - Apart from the issue of skin tolerance and level of comfort, water temperature does not appear to be a critical factor for microbial removal from hands being washed. In contrast, in a study comparing water temperatures of 4 °C, 20 °C and 40 °C, warmer temperatures have been shown to be very significantly associated with skin irritation. The use of very hot water for handwashing should therefore be avoided as it increases the likelihood of skin damage.

There are a number of studies that have looked into water temperature and handwashing and concluded that there is little to no added benefit to washing with hotter water, for example:

It's all about the technique

The CDC recommends using soap, scrubbing for at least 20 seconds, and rinsing under running water4. Based on the currently available scientific literature, it does not recommend using hotter water, as it does not seem to have an effect.

In short, scrubbing and using soap are far more effective for hand-washing than using hot water is.

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    My usual comment on this is that norovirus, which is definitely something you'll want to wash your hands for, is resistant to boiling/steaming. The only reason to turn the water up is if its too cold for you to keep your hands under the stream long enough to wash properly. – Fomite Apr 14 '15 at 14:34
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    @Fomite - I don't like to cross post; if you would have a look at this - since you mentioned norovirus specifically - it would be much appreciated. – anongoodnurse Apr 15 '15 at 2:03
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    @Nate - +1. Very nice answer. The skin damage hot water does is measurable; the effect of washing hands with hot water on reducing bacteria isn't! – anongoodnurse Apr 15 '15 at 2:06
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    @anongoodnurse On it. – Fomite Apr 15 '15 at 2:35
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Hot water in your water heater should be 140 degrees Fahrenheit to kill bacteria. Therefore your hot water is clear of bacteria. Noone could be able to tolerate washing hands in 140 degree water alone, but hot water mixed with cool water cleans better. Using soap is a must to wash away bacteria from skin surfaces. Wash all your laundry in hot water alone to clean and kill germs and bedbugs. Rinse in cool water. Laundry detergents and household cleaning detergents and disinfectants are more effective in hot water.

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    Legionnaire disease bacteria thrives in your hot water heater at temperatures less than 140 degrees Fahrenheit. So it is vital to keep the water temperature about 140 F to kill it and other bacteria/viruses as well. – S De Febles Feb 28 '17 at 4:40
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    Welcome to health SE :-). The person is specifically asking about washing of hands not clothes or surfaces. Also they are asking for a conformation of facts coming from an unverified source, and you offer no references, so this doesn't really answer the question. – Lucky Mar 6 '17 at 15:08

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