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Hand Washing: Separating the Science from the Myths

Keith Warriner
October 28, 2014

hand washingThere are many old-wives tails, rumors and stories that are so ingrained that we don’t know if they are fact or fiction. The list is so long that a popular TV show called “The Myth Busters” is totally devoted to applying science to verify if myths are true or false. The show is for entertainment but it is when myths or non-substantiated knowledge, are actually applied in regulations and guidelines with the thought that someone must have done the science at some point in time. With this in mind we see the method for hand washing posted everywhere from web sites to posters above sinks. However, we rarely pause to think about the scientific evidence to support the guide on effective hand washing.

 

Well, as many new mothers in the latter part of the 19th century will verify, hand washing has been an essential intervention for minimizing the transfer of pathogens in clinical, food and other environments. The recommended method for washing hands was developed in 1980’s and has not changed significantly through the years. But is the method supported by science?

 

Myth 1: Antimicrobial soap provides superior hand washing results compared to normal soap

 

It has been widely accepted that antimicrobial soap is preferred over normal soap for increasing the efficacy of hand washing. Of all the aspects associated with hand washing the comparison of antimicrobial vs normal soap has been studied to the greatest extent. The general conclusion is that antimicrobial soap supports a marginal increase in the number of bacteria removed from hands. If high inoculation levels are applied to hands then the removal with antimicrobial soap is statistically significantly compared to normal soap. However, with natural skin microflora there is no difference between the efficacy of normal and antimicrobial soap.  

 

There has been recent research that has suggested that antimicrobial soap can detrimental through disrupting the balance of the skin microflora and irritating the skin. On this basis all the evidence would suggest that antimicrobial soap has no advantages over normal soap.

 

Myth: Busted

 

Myth 2: Warm or hot water is better for hand washing than cool water

  

The FDA have reviewed the recommended water temperature used for hand washing no less than three times. The results of the deliberations was that 110F (43°C) should be set as the recommended temperature in the belief a greater proportion of microbes can be removed. However, all the scientific evidence available suggests that water temperature has no effect on the removal of microbes in the range of 4 -49°C. However, other research in this area has illustrated that water temperature does influence the duration of hand washing with cold or hot water leading to shorter rinse times due to user discomfort.  

 

Myth: Busted

 

Myth 3: Paper towels are perform better than air dryers

  

The method used for drying hands following washing is one of the most contentious issues in the hand hygiene arena. The general thought pattern when devising the hand washing guidelines was that hands needed to be dried to prevent acquisition of contamination from surfaces. This is true to a degree but it should also be noted that hand drying can contribute significantly in reducing microbial levels on hands following washing.

 

Watch the "Mythbusters" crack this myth

 

The majority of papers published to date have been pro-paper towels and even the “The Myth Busters” returned the same conclusion. However, it should be noted that many of the comparative studies performed the researchers used hot air hand driers that generated a gentle breeze making the user resort to completing the drying process using ones pants. More modern high speed (air blades) driers certainly can dry hands to the same extent as paper towels within 20 seconds. When a comparison is made between air blades and paper towels there is no difference in terms of microbial log reduction or degree of hand dryness. Given that high speed hand driers are not universally available, the evidence would support the view that paper towels are indeed better that hot air driers.

 

Myth: True

 

So does it matter if hand washing protocols are not science based?

It is apparent that many aspects of the hand washing protocol are not based on hard scientific evidence but this does not mean it is the wrong thing to do. Still, by reconsidering if anti-microbial soap is really necessary then skin health could be improved. The savings on energy and water usage by reducing the recommended wash time and temperature could also have a positive impact. Regardless of this, we always need to consider the science when devising guidelines.

 

Challenge us!

 

Submit your hand hygiene myths and we’ll put them up to the challenge and report our findings!

 

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