Does the five second rule really work?

Bacteria in Your Home: Germ Geography

Think a doughnut dropped on your sparkling kitchen floor might be edible with just a quick brush off? It might be -- if you'd have no problem eating something out of the garbage. A study from the Hygiene Council (sponsored by the company that makes Lysol) found that kitchen floor just in front of the sink has more bacteria (830 per square inch) than the trash can (411 per square inch). Other surprises included the fact that the sponge held 60 times more bacteria than the pet's food bowl and that the kitchen counter was more germy than the toilet seat [source: CBS News].

In fact, toilet seats get a bad rap all around. A recent study by Gerba has shown that they're not even the dirtiest place in the bathroom. That honor goes to the toilet paper dispenser, with more than 150 times the bacterial levels of the porcelain throne. The next most contaminated spot is the paper towel dispenser, which harbors 50 times more germs than seats [source: Reuters].

To further defend the commode, your cell phone carries 25,000 germs per square inch, while toilet seats hold only 344 bacteria in the same space -- and we all know how much time we spend with our mobiles pressed close to our mouths [source: Sinovic]. Among the germs clamoring to join our conversations are staph, found on nearly half of 25 random mobile phones tested by Gerba [source: ABC News Health].

When the "germ guru" turned his attention to another everyday item -- women's purses -- the results weren't any more encouraging. Through a small random field test, the numbers of bacteria found on the bottom of ladies' bags ranged from small numbers to the nation-sized amount of 6.7 million [source: Leamy].

Fortunately, most of the germs that are crawling around our desks, on our phones and beneath our bags are of the benign kind and are kept under control with basic hygiene. But people with compromised immune systems, or those who spend time in areas likely to be contaminated with E. coli or salmonella, should definitely think for at least five seconds before putting anything in their mouths that has touched the floor.

Related HowStuffWorks Articles


  • Fox, Maggie; O'Callaghan, John. "Mystery solved: How Bleach kills germs." Reuters. November 13, 2008. (Accessed August 11, 2009)
  • Sinovic, Emily. "Cell Phone Germs." October 30, 2008. (Accessed August 11, 2009)
  • CBS News Health. "Top Spots For Household Bacteria." June 25, 2007. (Accessed August 11, 2009)
  • McGee, Harold. "The Five-Second Rule Explored, or How Dirty Is That Bologna?" The New York Times. May 9, 2007. (Accessed August 11, 2009)
  • Heyamoto, Lisa. "The five-second rule is tough to swallow." The San Diego Union-Tribune. February 14, 2009. (Accessed August 11, 2009)
  • Fierer, Noah. "Women have more diverse hand bacteria than men, says CU-Boulder study." November 3, 2008. (Accessed August 11, 2009)
  • Smith, Sandy. "The Dirty Truth about your Desk." EHS Today. March 29, 2002. (Accessed August 11, 2009)
  • Reuters. "Research from Dr. Charles Gerba Finds Average Toilet Paper & Towel Dispensers Have More Bacteria Than Average Toilet Seat." June 17, 2009. (Accessed August 11, 2009)
  • ABC News. "What's Dirtier, Cell Phone or Toilet Seat?" August 4, 2006. (Accessed August 11, 2009)
  • Leamy, Elisabeth. "Your Purse Could Be Making You Sick." ABC News. August 8, 2006. (Accessed August 11, 2009)
  • Malof, Rich. "The Five-Second Rule." MSN Health and Fitness. (Accessed August 11, 2009)
  • Dawson, P; Han, I; Cox, M; Black, C; Simmons, L. "Residence time and food contact time effects on transfer of Salmonella Typhimurium from tile, wood and carpet: testing the five-second rule." Journal of Applied Microbiology. October 6, 2006. (Accessed August 11, 2009)
  • Agle, Merideth. "If You Drop It, Should You Eat It? Scientists Weigh In on the 5-Second Rule." Aces News. September 2, 2003. (Accessed August 11, 2009)
  • ABC News Health. "What's Dirtier, Cell Phone or Toilet Seat." August 4, 2006. (Accessed August 11, 2009)