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Using a dab of hand sanitizer to clean hands after sneezing in the car or before putting contact lenses on the train to work is cheap, quick, and convenient. But do hand sanitizers really work?

Keeping your hands clean — meaning as free from pathogens as possible — is one of the most effective ways to prevent the spread of infections. Thankfully, it's also quick and easy. But what's the best way to get germs off your hands? Should you choose soap and water, or are hand sanitizers an acceptable alternative to handwashing while you're out in public?

Is your hand sanitizer really sanitary?

For a hand sanitizer to kill bacteria, viruses, fungi, and parasites on contact, the key ingredient is Isopropyl alcohol. The alcohol kills infectious microorganisms in just seconds and quickly evaporates from the skin, but the product has to contain 60 to 95 percent alcohol. Some products don't.

That is why it is important to read the label. Your hand sanitizer absolutely must list alcohol as the first ingredient. If alcohol is the second-named ingredient, there is no way that the product contains enough.

When the hand sanitizer is only 40 percent to 50 percent alcohol, the only thing that using the product accomplishes is spreading bacteria around on the skin so that the whole hand is infected. Weaker concentrations of alcohol can actually increase the risk of infection.

Which is better, hand sanitizers or soap and water?

Most experts in communicable diseases agree that hand sanitizers should only be used when it is not possible to wash the hands for 15 seconds in warm water with a lather of soap. What washing the hands can do that using hand sanitizer cannot is removing essentially all the microorganisms on the hands so that they are rinsed down the drain.

Of course, there is a right way and a wrong way to wash the hands. It is not necessary to use a harsh detergent or to fill the wash basin with big bubbles of soap. Both detergent and big bubbles of soap can dry out the skin.

Many people hold their hands under water as if they were praying in church. Running water from fingertips to wrists spreads bacteria over the hands. A better way to wash the hands is to hold them as if waving goodbye to germs. This rinses bacteria and other pathogenic organisms off the fingertips into the sink so more bacteria can be removed for good.

What to do when handwashing is not possible

If you don't have running water, it's usually not practical to wash your hands. But there are situations when just a little water makes a big difference.

  • E. coli can form spores that stick to the hands. Using as little as 2 ml (about a teaspoon) of water, however, can increase removal of E. coli from the hands by 10,000 oercent. If you can't wash your hands after using the toilet, try at least to find a little water to run over your fingertips.
  • Rotovirus, norovirus, and other food contaminants are best removed by washing hands in soapy water for at least 30 seconds, following by drying with a clean towel (that is, one that is not shared with others and has not been used before). If washing is not possible, alcohol-soaked moist towelettes remove about 10 times more viruses than alcohol-based hand gel. Wipe from the base of the fingers to the tips without a backward motion.
  • When tap water is contaminated with sewage, it is better to use an alcohol-based hand cleanser. A study of women preparing foods in homes with contaminated tap water in Tanzania found that sanitizer removed three to four times as many bacteria as washing the hands in tap water, even with soap.

  • Pickering AJ, Boehm AB, Mwanjali M, Davis J. Efficacy of waterless hand hygiene compared with handwashing with soap: a field study in Dar es Salaam, Tanzania. Am J Trop Med Hyg. 2010 Feb,82(2):270-8.
  • Photo courtesy of singsinthecar on Flickr: www.flickr.com/photos/singsinthecar/2294337485/