Five-second rule

From Wikipedia, the free encyclopedia
Strawberries dropped on the ground. The five-second rule suggests that if they are picked up within five seconds, it is safe to eat them without rewashing.

The five-second rule, or sometimes the three-second rule,[1] is a food hygiene myth that states a defined time window after which it is not safe to eat food (or sometimes to use cutlery) after it has been dropped on the floor or on the ground and thus exposed to contamination.

There appears to be no scientific consensus on the general applicability of the rule,[2] and its origin is unclear.[3][4][5] It probably originated succeeding[clarification needed] germ theory in the late 19th century. The first known mention of the rule in print is in the 1995 novel Wanted: Rowing Coach.[6]


Portrait of Genghis Khan

The origins of the five-second rule is unclear. In the book Did You Just Eat That?: Two Scientists Explore Double-Dipping, the Five-Second Rule, and other Food Myths in the Lab food scientist Pawl Dawson and microbiologist Brian Sheldon trace the origins to legends surrounding Genghis Khan in the 15th century. Supposedly, the Mongol ruler is rumoured to have implemented the "Khan Rule" at his banquets. "If food fell on the floor, it could stay there as long as Khan allowed," and the idea was that "food prepared for Khan was so special that it would be good for anyone to eat no matter what."[7]


The five-second rule has received some scholarly attention.[8] It has been studied as both a public health recommendation and a sociological effect.

University of Illinois[edit]

In 2003, Jillian Clarke of the University of Illinois at Urbana–Champaign found in a survey that 56% of men and 70% of women surveyed were familiar with the five-second rule. She also determined that a variety of foods were significantly contaminated by even brief exposure to a tile inoculated with E. coli.[9] On the other hand, Clarke found no significant evidence of contamination on public flooring.[9] For this work, Clarke received the 2004 Ig Nobel Prize in public health.[10] A more thorough study in 2007 using salmonella on wood, tiles, and nylon carpet, found that the bacteria could thrive under dry conditions even after twenty-eight days.[11] Tested on surfaces that had been contaminated with salmonella eight hours previously, the bacteria could still contaminate bread and baloney lunchmeat in under five seconds. But a minute-long contact increased contamination about tenfold (especially on tile and carpet surfaces).[12]

Rutgers University[edit]

Researchers at Rutgers University debunked the theory in 2016 by dropping watermelon cubes, gummy candies, plain white bread, and buttered bread from a height of five inches (13 cm) onto surfaces slathered in Enterobacter aerogenes. The surfaces used were carpet, ceramic tile, stainless steel and wood. The food was left on the surface for intervals of 5, 30 and 300 seconds. The scientists assessed the amount of E. aerogenes transferred between surface and food. Since bacteria tended to be attracted to moisture, wet food had more risk to have bacteria transferred than dry food. To the surprise of the researchers, carpet transferred fewer bacteria than steel or tile. Wood was hard to pin down as it showed a large variation. "The five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food," Donald Schaffner, a Rutgers University biologist and an author of the research, stated in the Washington Post, "Bacteria can contaminate instantaneously."[13]

A pediatrician criticized the study for discounting the danger in consuming food after one touches other surfaces like refrigerator handles, light switches, and wallets, which have been found to be similarly contaminated with bacteria.[14]


A 2006 study at Clemson University was unable to verify the rule, when looking at tile, wood, and carpet floors. It indicated that bacteria can survive on the ground for a long time.[15]

A 2014 study by biology students at Aston University in England suggested that there may be a basis for the five-second rule.[16] Anthony Hilton, head of microbiology at Aston University, indicated in 2017 that food dropped on a seemingly clean floor for a few moments can be eaten with minimal risk.[17] According to Hilton, moist foods that are left on the floor for more than 30 seconds are contaminated with 10 times more bacteria than food that has been left on the floor for 3 seconds.[18]


The five-second rule was featured in an episode of the Discovery Channel series MythBusters, which discovered that there was no significant difference in the number of bacteria collected. The aspects that affect the contamination process is the moisture, surface geometry and the location.[19] An episode of Food Detectives found that bacteria will cling to food immediately.[20]


  1. ^ (7 February 2006) Getting the dirt of the 5-second rule, Southeast Missourian
  2. ^ Leanna Skanulis (2007). "'5-Second Rule', Sometimes". WebMD. Retrieved March 15, 2017.
  3. ^ Sefton, Dru (2003). Intern Puts Science Behind the Five-Second Rule, Newhouse News service
  4. ^ Kluck, Chad (2000). I Think Therefore I Am: A Collection of My Thoughts. Chad Kluck. p. 35. ISBN 9780533133246.
  5. ^ (16 May 2007). Kissing Away the Germs (letter to editor), The New York Times
  6. ^ Mayer, Johanna. "The Origin Of 'The Five-Second Rule'" Science Friday, 20 February 2019.
  7. ^ "The Origin Of 'The Five-Second Rule'". Science Friday. Retrieved 2024-04-14.
  8. ^ Julie Deardorff "Capsule: The five-second rule" Los Angeles Times, August 9, 2010, accessed January 18, 2011.
  9. ^ a b Picklesimer, Phyllis (2003-09-02). "If You Drop It, Should You Eat It? Scientists Weigh In on the 5-Second Rule". ACES News. University of Illinois College of Agricultural, Consumer, and Environmental Sciences. Archived from the original on 2015-09-14. Retrieved 2013-05-04.
  10. ^ "Improbable Research". Archived from the original on 2009-08-30. Retrieved 2008-04-24.
  11. ^ Dawson, P.; I. Han; M. Cox; C. Black; L. Simmons (April 2007). "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. 102 (4): 945–953. doi:10.1111/j.1365-2672.2006.03171.x. PMID 17381737. S2CID 19871846.
  12. ^ McGee, Harold (2007-05-09). "The Five-second Rule Explored, or: How Dirty Is That Bologna?". The New York Times. Retrieved 2007-05-09.
  13. ^ "The 'five-second rule' for eating food? Scientists just demonstrated how gross it is". Washington Post. Retrieved 2017-02-10.
  14. ^ Carroll, Aaron E. (October 10, 2016). "I'm a Doctor. If I Drop Food on the Kitchen Floor, I Still Eat It" – via
  15. ^ Anupriya, P.; Han, I.; Cox, M.; Black, C.; Simmons, L. (2007). "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. 102 (4): 945–953. doi:10.1111/j.1365-2672.2006.03171.x. ISSN 1364-5072. PMID 17381737. S2CID 19871846.
  16. ^ "Researchers prove the five-second rule is real". Aston University.
  17. ^ Ryan Hooper (March 15, 2017). "'Five-second rule' for food dropped on the floor approved by germ scientists". The Independent (UK). Retrieved March 15, 2017.
  18. ^ Greenemeier, Larry. "Fact or Fiction?: The 5-Second Rule for Dropped Food". Scientific American. Retrieved 2023-05-02.
  19. ^ "Annotated Mythbusters: Episode 39 Chinese Invasion Alarm, 5 Second Rule". Retrieved 2008-08-17.
  20. ^ "Food Detectives, Episode OF0101". Archived from the original on 2011-05-06. Retrieved 2011-01-31.