Thursday, October 9, 2014
With flu season upon us and the constant (media) threat of an Ebola outbreak, it’s an excellent time to discuss hygiene strategies, especially those that help ward off infectious diseases. The most common advice you’ll likely hear is to frequently clean your hands with soap and water and/or hand sanitizer. Either method can be quite effective at preventing the spread of infectious diseases if used properly, but I’ve met some people that just love hand sanitizer and use it exclusively without ever using soap, and this can be problematic.
Hand sanitizer contains the active ingredient ethanol (same alcohol found in liquor) which kills bacteria by disrupting their outer cell membrane (lysis). Hand sanitizer does not kill viruses (since viruses are not living organisms, though this topic is often debated), but importantly hand sanitizer does inactivate most viruses, making it a useful option to prevent the spread of viral infections.
Hand sanitizers often vary in alcohol concentration, and this can drastically impact its effectiveness. Typically, the higher the alcohol percentage, the more antiseptic it is. For example, gels containing less than 50% ethanol may be less effective than gels containing over 60% ethanol. You can also find alcohol-free hand sanitizers, but these contain anti-bacterial agents (triclosan, for example) which are not effective against viruses and are believed to contribute to the growing abundance of antibiotic-resistant bacteria. I plan to write more about this topic when I discuss anti-bacterial soap in the near future.
Several studies have shown that the proper use of hand sanitizer can significantly reduce the chance of getting sick, particularly during flu season. For example, a study published in June 2014 demonstrated that students who used hand sanitizer regularly each day in addition to regular hand washing with soap and water were significantly less likely to miss school due to illness compared to students that only used soap and water to wash their hands. This isn’t to say that hand sanitizer is superior to soap and water washing, but hand sanitizer can often times be more convenient, especially in situations where a sink is not readily available.
However, it is important to note that there is a significant difference between washing and sanitizing. Hand sanitizer only sanitizes, meaning it typically removes > 99.9% bacteria and viruses if used properly. But what about dirt? Grease? Toxins? Metals? Dust? Fecal matter? Any other contaminant you can think of that comes into contact with your hands?
Washing with soap and water is effective at removing all of these things. Soap is not inherently anti-bacterial, but rather it is the emulsion that forms during hand-rubbing in water which acts as the “cleaning” mechanism. This is why rubbing your soapy hands together for at least 20 seconds is critical because the fats in soap form micelles which trap bacteria along with all the other contaminants on your hands, and the water rinse at the end washes it all away.
Therefore, I believe hand washing with soap and water should always be a first option if readily accessible and convenient since it eliminates bacteria, viruses, and more when performed properly. Alcohol-based hand sanitizer is an excellent second choice, but it should not be used exclusively for all of your hand cleaning needs.
 Azor-Martinez et al. Am J Infect Control. 2014 Jun;42(6):632-7