How Do Hand Sanitizers Work?

Since 2002, the Center for Disease Control (CDC) has recommended the use of alcohol-based hand sanitizers in hospital settings as a supplement to regular hand washing. This recommendation, combined with a few public health scares, has led to increased popular use. But to be effective, hand sanitizers must be used properly, and to use them properly, it helps to understand how they work.

Hand sanitizers work by using a high concentration of alcohol to kill bacteria on the surface of your hands. The alcohol penetrates the cell membrane of the bacteria and denatures it (meaning it changes the nature of the bacteria, making it inert) by not allowing the proteins to fold properly. It simultaneously strips the outer layer of oil off of your hands, creating an inhospitable environment for new bacteria. By rubbing enough alcohol over the surface of your hands for a short period of time, you allow the alcohol to make contact with, and destroy, most of the bacteria on your hands.

Effective Use

Choose a hand sanitizer that has a high concentration of alcohol. The CDC recommends using a concentration of 60 percent to 95 percent ethanol or isopropanol alcohol, as their formal hand-washing trials have proven this to be the most effective. In fact, in the March 21, 2006, issue of The New York Times, Scott Reynolds, a specialist in infection control at the James H. Quillen Veterans Affairs Medical Center, comments on his study that suggests lower concentrations of alcohol seemed almost worse than not using hand sanitizer at all: "If anything...the faulty gel seemed to mobilize the bacteria, spreading them around the hand instead of killing them." Be sure to turn the bottle around and read the label, as almost all hand sanitizers claim they kill 99.9 percent of bacteria and germs even when they have a lower concentration. Use at least a dime-sized dollop, and rub it briskly all over your hands for 30 seconds. If the hand sanitizer dries in before 30 seconds, you have not used enough for it to be effective.

Effectiveness Against Dirt

If your hands are visibly soiled, the alcohol in your hand sanitizer is not going to wipe the dirt away for you. Hand sanitizers work best when they easily can get to the bacteria on hands that are relatively clean (such as in a hospital setting) to begin with, so if you can see the dirt on your hands, regular hand washing is strongly recommended instead. If you do not have access to soap and clean water, however, using a hand sanitizer is better than nothing.

Effectiveness Against Fecal Matter

Similarly, hand sanitizers are not recommended for sole use after using the bathroom, as they will not remove fecal matter. Worse, they may not even be able to kill the bacteria in the fecal matter that is still on your hands. According to the experts in back-country hygiene at REI, "Clostridium difficile, a spore-forming bacterium sometimes found in fecal matter, is resistant to sanitizers and requires hand washing for removal."

Effectiveness Against Viruses

Finally, the question of whether hand sanitizers are useful against viruses is one that needs more study. The alcohol in hand sanitizers will not kill viruses, but it will make the surface of your hands a less hospitable environment for them, making it less likely they will stick around.

References

• Franklin, Deborah. "Hand Sanitizers, Good or Bad?" The New York Times 21 March 2006.
• The Center for Disease Control
• R.E.I. Backcountry Hygiene and Sanitation

Resources

• FDA's HANDWASHING-RELATED RESEARCH FINDINGS
• The Center for Disease Control's Clean Hands Save Lives: Emergency Situations