"Now wash your hands." For years public health officials have relied on such well-worn exhortations to persuade the rest of us to rinse with soap.
But their pleas are often ignored. A 2011 study found that, while 95 per cent of Britons claim to wash their hands after visiting the bathroom, barely a tenth actually do.
The World Health Organisation's new plan is to scare soap-dodgers into submission, with the release of a new series of "hand scans" designed to highlight the invisible effects of bad hygiene.
The images will leave few in any doubt, revealing disturbing levels of bacteria on unwashed fingers after a series of tasks such as cutting chicken, handling an old dishcloth or going to the toilet.
Happily, the photographs have been published alongside another set of images of showing how easily the bacteria can be removed with a simple wash in the sink.
The publicity campaign coincides with Global Handwashing Day, an international awareness campaign that aims to spread the message of how the simple act of washing your hands with soap can reduce the spread of fatal diseases including E.coli and the winter norovirus.
The spread of these illnesses poses a major threat to public health, policy makers say, asserting that soap could save more lives than any single vaccine or other form of medical intervention.
Dr Paul Cosford, Director of Health Protection at Public Health England (PHE), which has supported the campaign's launch, said: "If we don't wash our hands properly then just one bacterium can grow into hundreds and thousands in a relatively short space of time.
"These are then spread around our environment and onto other people.
"This is why it is so important that we wash our hands thoroughly particularly before preparing food, after handling raw meat and after going to the toilet."
Failure to wash hands after visiting the toilet is thought to have fuelled the spread of recent viruses such as the winter vomiting bug, which travels from person to person through a process doctors call the "faecal-oral route".
A study carried out by the London School of Hygiene and Tropical Medicine three years ago revealed that more than nine out of 10 mobile phones are coated with some kind of bacteria, including E.coli and MRSA.
Peter Hoffman of PHE, added: "Just as contamination was passed from my hands to the growth surfaces in the pictures, so it could be passed from your hands to your mouth, the food that you handle or any other route of infection.
"Washing the hands using soap and water is integral to breaking the cycle of transmission of harmful bugs, whether that is in a hospital or in our own homes and everyone needs to adopt this very good habit."
The awareness campaign comes just weeks after nurses were reminded to wash their hands in the wake of new NHS guidance warning that the levels of infection in UK hospitals are "unacceptable and avoidable".