It’s Global Handwashing Day! (Do you know where your soap is?)

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Today, Global Handwashing Day is being celebrated in 70 countries around the world, with ritual hand-washing clinics, children singing about the disease-preventing benefits of hand-washing and, of course, a heartwarming study to explore what messages work best in promoting the use of soap in hand-washing. (Because -- join in with me here -- water doesn’t kill germs; soap does!)

Researchers from the London School of Hygiene and Tropical Medicine spent several months leading up to last year’s Global Handwashing Day peering through a camera’s lens at men and women using a service station’s restroom at a major crossroads in Britain. Their challenge: to gauge not only how many people actually use soap when they wash their hands, but also what messages -- flashed onto LED screens at the entrance to the toilets -- will most effectively induce people to use soap when they wash their hands?

They have gleaned these truths about men, women and hand-washing.

Men are basically gross: Fewer than a third of them (32%) used soap when they washed their hands -- and those were the ones that actually washed their hands. And they responded best to hand-washing-reminder messages that invoked disgust, such as ‘Wash it off now or eat it off later.’ Eeeuw.

Women are not as gross, though there is room for improvement. Fully twice as many women (64%) used soap. And women seemed especially receptive to messages that were ‘reminders’ of good-hygiene measures they were presumed to know already, such as the always appropriate ‘Water doesn’t kill germs....’ (In fact, any messages that included the word ‘germs’ were the most successful in inducing soapy hand-washing in women, but least successful in doing so in men.)

The most effective message in inducing people to use soap in washing their hands was, ‘Is the person next to you washing with soap?’ The authors of the study, published in the American Journal of Public Health, suggest that this message appeals to a viewer’s sense of shame: If the person next to me is paying attention, I’d better not get caught dirty-handed.

This blogger has to wonder whether the two genders do not process this message differently as well: For men, ‘Is the person next to you using soap?’ may be an invitation to a contest in the cleanliness arena; for women, it may be a reminder that one must set the right example to those who will be watching.

Either way, in these days of novel H1N1 flu and all manner of predatory pathogens, the message is clear: Celebrate hand-washing day every day -- use soap! Here’s a boring government-issued primer on how best to do it, but you can check this funky version out, or better yet, tune in to this one from Bill Nye the Science Guy. And a recent New York Times article explores the oft-asked question: Is hot water better than cold?

-- Melissa Healy