Hot or Cold Water?

My brother was doing dishes with me when he asked why we used hot water to wash dishes and our hands rather than cold water.  I had never really thought about it.  The answer that every Mom I know of has given is that you use hot water to kill germs.  But that’s not true.  Water hot enough to kill the majority of germs would also give you massive burns.

The shock that I got when I did a search online was that people didn’t know this.  There were people saying you should wash with cold to kill germs, hot to kill germs, warm, not hot, because it kills better, etc…  Washing your hands with soap and water is the number one way to avoid disease transmission, but people don’t know why.

So why do we wash in hot water?  I thought about the idea for some time and came up with two reasons for my brother.  The first and probably most important is that the heat helps melt grease or fats and allows the soap to be more effective.  The second is comfort.  I’d rather put my hands in hot water than cold.  Washing has nothing to do with killing germs, but washing them off.  The point of washing your hands thoroughly is that you wash the germs off, not kill them, and if you don’t scrub every area with soap and rinse thoroughly they stay, especially in crevices like your nails.

As for antibacterial soap, just remember that the purpose of washing hands is to wash off bacteria not kill it.  Antibacterial soap is not any more effective at washing, and has to be left on for 2 min in order to be effective at killing. Also there is merit to the idea that using antibacterial soaps and detergents contribute to “super bugs.”

Proper hand washing is effective for disease control.  Practice it your self and teach it to your children.  If you do not have soap and water, the next best thing is an alcohol based hand sanitizer.  For tips on how to best wash your hands here is the Center for Disease Control (CDC) and another great site.


One thought on “Hot or Cold Water?

  1. Trishelle

    Hmmmm. Thanks for the scoop, Dr. Duncan. From now on, I will not be loading my kids up with disinformation. 🙂 I will, however, still advocate handwashing with warm water to wash off germs and break down oils since my kids still like to stick their hands in places germs love to thrive in.

    Handwashing still requires the same pattern, I just know more about the ins and outs.


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