Handwashing is the single best way to prevent colds and many other infectious diseases—as long as you do it right. Soap and water, along with the friction of rubbing your hands together, loosens dirt and creates a slippery surface so germs slide off.
You should wash your hands often, before and after eating or preparing food (particularly raw meat, fish, and eggs), after using the toilet, after blowing your nose, after changing a diaper, after playing with pets or cleaning up their waste, before and after touching someone who is sick or treating a wound, before putting in contact lenses, and after gardening.
How long should it take you to wash your hands?
If you follow recommendations from the Centers for Disease Control and Prevention (CDC), you’re supposed to lather up and rub all surfaces of your hands together for 20 seconds—the time it takes to sing “Happy Birthday” twice. According to the World Health Organization, the whole process, from washing to drying your hands, should take 40 to 60 seconds.
Does the water temperature matter?
A few studies suggest that water temperature has no significant effect on reducing bacteria under normal handwashing conditions. The latest study, in the Journal of Food Protection in June 2017, involved 20 volunteers who, after having their hands contaminated with a nonpathogenic strain of E. coli bacteria, washed their hands under different conditions, including varying water temperatures (100°, 80°, and 60°F). As in previous studies, the cool water was just as good as warmer water in reducing microbial load.
Hotter water does cut through oil on your hands faster, but cooler water will also do the job. Hotter water does cut through oil on your hands faster, so they may feel cleaner. But very hot water can also damage skin, making it more susceptible to colonization by bacteria, which are then harder to remove. Hotter water also uses more energy. So washing with cooler water is not only as effective, it’s also more energy-efficient.
How should you dry your hands?
Drying your hands reduces bacteria levels further, but it’s debatable whether using paper or cloth towels or a warm-air dryer is best. A study from the Mayo Clinic in 2000 found no differences between these methods in terms of removing bacteria from hands; other research suggests paper towels are more effective. If you use a dryer, keeping your hands still removes more bacteria than rubbing them together.
The new ultra-rapid dryer, the Airblade, is an efficient way to dry your hands: According to a recent study funded by the manufacturer, it removes as much bacteria in 10 seconds as a conventional dryer does in 30 seconds. Whichever method you use, the key is to make sure your hands are fully dry—hands that remain wet are more likely to transfer bacteria to and from the next surface you touch.
Is hand sanitizer a good substitute?
Handwashing is generally preferable, but alcohol-based hand sanitizers are a convenient option when soap and water are not available. They kill most bacteria and viruses on contact, but not bacterial spores. Look for products with at least 60 percent alcohol (ethanol and/or isopropanol).
Dirt, food and other grime on your hands make the alcohol in hand sanitizers less effective, however, so if your hands are visibly dirty or greasy, you’re better off washing them. Handwashing is also recommended instead of sanitizers after going to the bathroom and before and after handling food. If you use a hand sanitizer gel, rub about a dime-size amount over all the surfaces of your fingers and hands until they are dry.
What about antibacterial soaps?
Soaps that contain antibacterial agents (most commonly, triclosan) kill or inhibit bacteria, as well as help physically remove them. But in September 2017, the FDA issued a final rule banning 19 antibacterial ingredients, including triclosan and triclocarban, from body washes and soaps. The agency cited a lack of evidence that antibacterial wash products work any better than plain soap and water, as well as data suggesting that long-term exposure to the active ingredients in such products may contribute to antibiotic resistance or cause hormonal effects. We warned back in 2014 that antibacterial soaps may do more harm than good.
What should you do if you can’t wash your hands?
The aim of washing is to get the germs off your hands so that they won’t get into your body (or be passed on to others). If you can’t wash your hands right away—and if you don’t have hand sanitizer—take special care not to rub or scratch your eyes or nose or touch your mouth.
Originally published June 1, 2011. Updated March 30, 2018.