A new scientific look at the five-second rule

(MEDSTAR) - How long does it take germs to hitch a ride on food after you drop it on the floor? Here's a hint - don't blink.

How many times can a baby drop a sippy cup to the floor? Plenty! But no worries. If mom picks it up within five seconds, it's germ-free. Right?

"Go ahead kid, it's the five second rule. It's not five seconds, pick it up and eat it. And i was told that. Everyone was told that. You know, it's just common, sort of, wisdom," said Scott Kelley, a microbiologist at San Diego State University.

Is it wisdom or a lot of hooey? To find out, San Diego State researchers dropped food items like carrots and sippy cups on highchair trays, countertops and floors.

"We picked them back up again within five seconds. Then, we swabbed off whatever surface it was and we put it on what was standardly called Petri plates where you can grow bacteria. Almost everything had, within five seconds, had some bacteria that were growable," Kelley said.

What they found was no surprise to scientists who study micro-organisms.

"I don't know what people were thinking," said Kelley. "Like you drop it in there and then the bacteria start running towards it? No!"

Kelley says bacteria are everywhere. You can't avoid them. While it sounds creepy, most are harmless. Some bacteria are even good for your health.

"It's only a few ones that you occasionally have to worry about and almost always, they come to someone who is already sick," Kelley said.

To protect your family, you should keep surfaces clean.

"Clean down surfaces with, you know, ethanol or bleach or something like that," said Kelley.

That way if you follow the five-second rule, you can reduce the spread of disease.

The five-second rule research was sponsored by Clorox. In a survey by the company, 65 percent of parents said they follow the five-second rule.

Fast facts:

  • More than 10,000 different species of bacteria are known to exist in the world.
  • In one survey, 65 percent of American adults believe in the "five-second rule."
  • Researchers tested contamination of various dropped objects picked up within five seconds.
  • The amount of bacteria picked up from each surface varied considerably.

For general information on germs and staying healthy:

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