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Recently published research from the University of Auckland shows you can get your hands clean without soap under running water.
However, as senior research fellow with the university's department of medicine Dr Tom Miller says, it is not a matter of putting your hands under the water briefly and flicking them dry.
You must hold them under running water and rub them together "purposefully" for 20 seconds - about the same time as a verse or two of a well-known song.
That did not mean "taking your skin off", nor did it mean casually waving one hand over the other. It involved friction - rubbing hands together backwards and forwards with some pressure between the fingers and involving both the palms and backs of the hands.
It was then important to dry the hands properly. Ideally this would involve 10 seconds drying the hands on a cloth or paper towel followed by at least another 10 seconds under an air drier.
However, if this were not possible, the next best option was two dryings on cloth or paper towels - the first to remove the bulk of the moisture and the second to finish the process.
Earlier research had shown drying hands adequately using an air drier alone took about 45 seconds, something most people were unlikely to do.
The recent research, published in Australian journal Healthcare Infection, involved 11 of his colleagues who volunteered to use three different ways of hand-washing after they had been contaminated with a saline suspension of E. coli bacteria from their own faeces.
The three hand-washing protocols involved holding hands under tap water, rubbing hands together as described above under running water without soap and then similar action with soap.
They were then required to touch items representing skin and food to determine how much contamination had been removed. A total of 330 samples were analysed.
The researchers found running water by itself was comparatively ineffective and that the hand-to-hand friction during washing had the biggest effect on reducing contamination.
In the first five to 10 seconds of the washing process they found soap actually slowed the process of decontamination, which they considered was due to the fact soap is a lubricant and therefore affected the amount of friction. Once the 20sec stage of the wash had been reached, the friction effect was restored because the soap had been washed off.
Soap only marginally improved the results at the end of the full 20sec friction wash.
Dr Miller said the message from the research was for people to realise that because there was no soap around it did not mean that they could not effectively decontaminate their hands, but it did take time.
Putting hands under water for a few seconds and not drying them properly was "not only useless, but also counter-productive".
If there is no means of hand drying available in a public toilet, drying hands on clothing would be better than nothing, but likely to be relatively ineffective. It would be better to carry a flannel or small hand towel or a pack of absorbent tissues, Dr Miller said.
Tissues could also be used to grip door handles on leaving as these were likely to be heavily contaminated.
Six 20sec songs to wash your hands by. -
• Happy Birthday (2 verses).
• Row Row Row Your Boat (2 verses).
• You are My Sunshine (1 verse).
• Twinkle Twinkle Little Star.
• God Save the Queen.
• Old McDonald had a Farm (1 verse).