Wash your hands. Yes, yes, we all know we should do it, especially after using the washroom.

But how many of us actually do? Not many, it seems.

Researchers from Michigan State University have just published a study that found that only five per cent of people who use bathrooms in restaurants and other public areas actually washed their hands afterward long enough to kill germs. That means a good 95 per cent of us are walking out of the bathroom with unclean hands.

The findings were made by student volunteers who were told to wait in restrooms in bars, restaurants and other public establishments to record whether people using the washroom were washing their hands afterward.

The students were told to be as unobtrusive as possible, so they would stand to one side, playing with their phones, while secretly recording data.

In all, the dozen volunteers made observations of 3,749 men and women. They found that 10 per cent of washroom users didn't wash their hands at all. Another 33 per cent didn't use soap.

Of the remaining people who did sud up at the sink, only a handful took the full 15 to 20 seconds needed to do a thorough job, according to the infectious disease experts at the U.S. Centers for Disease Control and Prevention.

The study found people washed their hands for only about six seconds, on average.

Other findings included:

  • Fifteen per cent of men didn't wash their hands at all, compared with 7 per cent of women.
  • Only 50 per cent of men used soap, compared with 78 per cent of women.
  • Hand-washing was more common earlier in the day than in the evening.
  • People were more likely to wash their hands if a sign encouraging them to do so was present.

Lead investigator Carl Borchgrevink, an associate professor of hospitality business, says the findings were surprising.

"There's a lot of dirty hands out there," he remarks in a video prepared by Michigan State.

Borchgrevink notes that hand washing is the single most effective thing one can do to reduce the spread of infectious diseases.

"It's essential to wash your hands because 50 per cent of all foodborne illness has been tied back to unclean or unwashed or improperly washed hands," he said.

As well, the former chef and restaurant manager says those who operate restaurants and hotels should take note of his study's findings.

"Imagine you're a business owner and people come to your establishment and get foodborne illness through the fecal-oral route -- because people didn't wash their hands -- and then your reputation is on the line," he said. "You could lose your business."