Eve Glazier, Elizabeth Ko | color

DEAR DOCTOR,

Why do you have to wash your hands with soap and warm water for at least 20 seconds? Are they not getting clean if you’ve only got cold water? And why is 20 seconds the magic number? What about hand sanitizers?

— THE GREAT UNWASHED

DEAR UNWASHED,

Handwashing is in the news right now due to the coverage of the new coronavirus, COVID-19, as well as our ongoing flu season.

It’s an important topic because, although the exact means of transmission of the new coronavirus isn’t clear yet, we do know how influenza spreads, and COVID-19 is likely to be similar.

In addition to inhaling aerosolized droplets from an infected person’s cough or sneeze, influenza spreads through contact with surfaces that have been contaminated by the virus. This can be direct contact, such as when you shake hands with someone infected with the virus, or indirect contact via a contaminated surface or object.

If you come into direct contact with the virus and then touch your own mucous membranes, you risk infecting yourself. This includes rubbing your eyes, nose or mouth; biting your nails; eating with your hands; dabbing on makeup; or just resting your chin in your hands.

All of this leads to two bits of important advice — don’t touch your face, and do wash your hands. The first relies on awareness, while the latter is all about technique.

Start by wetting your hands with clean, running water. The temperature of the water doesn’t play a role in efficacy; it’s just that warm water is more comfortable to use. If cold water is the only option, that’s fine. What matters most is that you work up a lather with soap — any kind of soap will do — and carefully clean all of the surfaces of your hands. Be sure to wash the palms and backs of the hands, the fingers, the knuckles, the webs between the fingers and the areas around and beneath the nails.

Doing this carefully and thoroughly, with gentle pressure to create friction, takes in the neighborhood of 20 seconds. Then rinse well and dry thoroughly. Frequent handwashing can dry out the delicate skin on your hands, so carrying a travel-size moisturizer can be a good idea.

As for hand sanitizers, studies have shown that although they can be helpful, washing with soap and water is the most effective at removing a variety of pathogens. Hand sanitizers may not be as effective when used on hands that are dirty or greasy.

When using a hand sanitizer, it’s important to choose one that is alcohol-based, at a concentration of no less than 60%. The product label will state the concentration of alcohol. Don’t skimp. Always use the amount of sanitizer that the label recommends. Then spread the liquid over all of the surfaces of your hands and rub gently until they are dry.

Hands clean? You’re not quite done yet. There’s another object that that makes frequent contact with your hands and face — your phone. Check manufacturer directions, and add cleaning your phone to your daily routine.

Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.

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