Damp hands spread bacteria
Failure to dry hands thoroughly after washing could increase cross-contamination, says study
Hand-hygiene is a key element in infection control and drying hands after washing is a very important part of the process. Not drying hands thoroughly after washing them could increase the spread of bacteria and rubbing hands together while using a conventional electric hand dryer could be a contributing factor.
A study by researchers at the University of Bradford and published in the Journal of Applied Microbiology looked at different methods of hand drying, and their effect on transfer of bacteria from the hands to other surfaces.1 The different methods included paper towels, traditional hand dryers, which rely on evaporation, and a new model of hand dryer that rapidly strips water off the hands using high velocity air jets.
When hands are washed the number of bacteria on the surface of the skin decreases, but they are not necessarily eliminated. If the hands are still damp then these bacteria are more readily transferred to other surfaces.
In this study the researchers quantified the effects of hand drying by measuring the number of bacteria on different parts of the hands before and after different drying methods. Volunteers were asked to wash their hands and place them onto contact plates that were incubated to measure bacterial growth. The volunteers were then asked to dry their hands using either hand towels or one of three hand dryers, with or without rubbing their hands together, and levels of bacteria were re-measured.
The researchers found that rubbing the hands together while using traditional hand dryers could counteract the reduction in bacterial numbers following hand-washing.
Furthermore, they found that the relative reduction in the number of bacteria was the same, regardless of the hand dryer used, when hands are kept still. When hands are rubbed together during drying, bacteria that live within the skin can be brought to the surface and transferred to other surfaces, along with surface bacteria that were not removed by hand-washing.
The study found the most effective way of keeping bacterial counts low, when drying hands, was using paper towels. Among the electric dryers, the model that rapidly stripped the moisture off the hands was best for reducing transfer of bacteria to other surfaces.
The full article is can be downloaded here.
Reference:
1. Snelling, A.M., Saville, T., Stevens, D. and Beggs, C.B. (2010) Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers. Journal of Applied Microbiology, doi: 10.1111/j.1365-2672.2010.04838.x
