Please rub your handsby Margo White
Thought the best way to wash your hands involved soap? Actually a Hail Mary and plenty of friction does the trick.
Chances are if you visit a public rest room over the summer, there’ll be no soap left in the soap dispenser. Never mind – latest news from the world of hand hygiene research reveals you don’t need soap to eradicate the invisible bacteria lurking in the palms of your hands. Rather, the crucial variable in a good hand wash is the friction generated by rubbing your hands together.
This is according to Dr Tom Miller and colleagues at the University of Auckland. Millar has become one of New Zealand’s leading luminaries on hand hygiene, at least since 1997, when he published a study that showed washing one’s hands was a redundant exercise if it wasn’t followed by thorough drying. Moisture, he pointed out, is a “microbial mobiliser”, and a damp hand provides an ideal environment in which bacteria can be passed on and picked up.
He followed that up with studies in which he compared the hand-drying resources available in the typical public toilet – paper towels, cloth towels and air dryers – to see which worked best. (The short answer: towels followed by 10 seconds under an air dryer.)
Having researched the complexities of hand drying, and influenced public health campaigns all over the world, and perhaps even the facilities provided in a few public rest rooms, Miller recently turned his attention to hand-washing. The area was ripe for investigation, he says. “You might think that would have been worked over, but when we went to look at the literature, just about all the instructions were based on intuition, on what seems about right, rather than any facts.”
And so Miller and his team drew on the volunteer services of colleagues who were willing to be contaminated with a sample of their own E coli – unsurprisingly, people have less objection to being contaminated with their own bugs than somebody else’s. He then got them to enact three possible scenarios: holding their hands under the tap for a period of time; rubbing their hands “purposefully” under a tap without soap; washing their hands as they normally would with soap and water.
“After two years of jolly hard work” they found that holding one’s hands under running water is a waste of time, but rubbing hands together “purposefully” under a running tap is extremely effective. After 10 seconds of rubbing, 95% of the microbes had been removed. After 20 seconds, 99% had gone. Interestingly, soap slowed down the rate of decontamination, at least initially, as soap decreases the friction. “But after about 20 seconds you ended up at the same point because you had got rid of the soap and the friction value was restored.”
Miller is reluctant to suggest that we abandon soap altogether. It’s useful when we have visible muck on our hands, as it gets rid of grease and dirt in a way that water doesn’t. But most of the time we wash our hands to get rid of that which we can’t see, in which case soap may not be imperative. “I think the value of using soap is that you tend to keep hands under the tap for longer, so we wouldn’t discourage using it. But the message is that you don’t need soap to decontaminate.”
This conflicts with the message most of us grew up with, as well as with what is promoted by soap manufacturers and marketers who have seized upon the profile hand hygiene has received in recent years (bolstered by the odd flu pandemic) and have developed all sorts of products as a result. Such as all those fashionable anti-bacterial soaps. “They have very little to offer above a normal soap,” says Millar, going on to point out that disinfection takes time. “The average hand wash is 20 seconds. There’s no way an antibacterial can act in that time.”
Alcohol-based gels and wipes have their merits, when there isn’t any alternative, but he also points out they need to kill the micro-organisms to be effective, so it’s generally more efficient to wash them away. “I think their principal advantage is they do dry the hands out, so you’re not going to be transferring and picking up microbial contaminants.”
In other words, it’s time to revise our understanding of what makes a good hand wash; use soap if you want, but focus on the friction. Miller recommends rubbing hands and fingers together under running water for 20 seconds. Asked whether anyone is really likely to count to 20 while rubbing their hands together, he suggests a Catholic approach. “Just say a Hail Mary. Slowly.”
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