Is the five-second rule a myth?

  • Article by: Chanie Kirschner
  • Mother Nature Network
  • September 18, 2013 - 3:40 PM


Everyone has heard of the five-second rule. You know the one: If a food item drops on the floor and you pick it up within five seconds, it’s still perfectly safe to eat. Undoubtedly invented by a child or teenager anxious to eat the last bite of dessert accidentally dropped on the floor, the five-second rule has been accepted and employed by kids and adults just about everywhere.

You’ll be dismayed to find out that the rule doesn’t have much scientific credence. You read that right — that Hershey Kiss you dropped on the floor while you were reading this article? Not as clean as you may assume it to be after having picked it up and popped it in your mouth a mere three seconds after it fell on the floor. (Of course your floor is clean enough, right? Right?)

High school student Jillian Clarke disproved this rule in 2003 during an internship at the University of Illinois. She found that food picked up E. coli bacteria as soon as it was dropped on a contaminated surface. (Interestingly, she also discovered that women are more likely than men to eat food that fell on the floor.) The motivated student’s research earned her an Ig Nobel Prize at Harvard University in 2004, awarded to scientists whose research “first makes you laugh, then makes you think.”

In 2007, researchers at Clemson University in South Carolina took the research a step further to determine whether leaving food on the floor longer actually meant more germs would attach to its surface, and whether different types of floors carried more or fewer germs. Their findings? Not pleasant. They found that bacteria such as salmonella can thrive on such floor surfaces as hardwood, tile and carpet for as long as four weeks. They also found that food dropped on these surfaces can pick up anywhere from hundreds to thousands of bacteria. When left for an even longer period, say, a minute? The number grew to 10 times that amount.

Another interesting point to note: Dr. Charles Gerba, a microbiologist at the University of Arizona, found in his studies that 93 percent of our shoes contain fecal bacteria on them. That’s because we’re walking everywhere in them — in the grocery store, the parking lot, even the public restroom. And if you wear your shoes in your house, where do you think that fecal bacteria is landing? You bet — right on your kitchen floor. Yet another reason to toss that tasty snack that landed on the floor.

Bottom line: Even though you may not like it (and you may hear your mother in your ear telling you not to waste food), better to toss the fare from the floor into your garbage can than into your mouth.

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