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{{short description|Western cultural food hygiene myth}}
{{for|the basketball rule|Five-second rule (basketball)}}
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[[File:Spilled_strawberries.jpg|thumb|[[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''', is a [[food hygiene]] [[urban legend]] 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.

While the amount of microbes transferred to a dropped food does increase over time, and in some situations floors may be relatively clean of pathogens, the scientific consensus is opposed to such a general applied rule,<ref>{{cite web |author=Skanulis |first=Leanna |date=2007 |title='5-Second Rule' Rules, Sometimes |url=http://www.webmd.com/a-to-z-guides/features/5-second-rule-rules-sometimes-#1 |access-date=July 10, 2024 |publisher=[[WebMD]]}}</ref> and the origin of the idea is unclear. It is speculated to have originated from legends about [[Genghis Khan]]. It was first mentioned in print in 1995.

== History ==
[[File:YuanEmperorAlbumGenghisPortrait.jpg|thumb|upright|[[Genghis Khan]] is said to have ruled that food dropped on the floor "could stay there as long as Khan allowed"]]
The origins of the five-second rule are unclear.<ref>{{Cite news |last=Sefton |first=Dru |date=September 29, 2003 |title=Intern Puts Science Behind the Five-Second Rule |url=http://www.newhousenews.com/archive/sefton092903.html |url-status=dead |archive-url=https://web.archive.org/web/20061115101748/http://www.newhousenews.com/archive/sefton092903.html |archive-date=November 15, 2006 |work=[[Advance Publications|Newhouse News Services]]}}</ref> Food scientist Pawl Dawson and microbiologist Brian Sheldon have traced the origins to legends surrounding [[Genghis Khan]] in the 15th century. He 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."<ref>{{Cite web |last=Mayer |first=Johanna |date=February 20, 2019 |title=The Origin Of 'The Five-Second Rule' |url=https://www.sciencefriday.com/articles/the-origin-of-the-five-second-rule/ |access-date=July 10, 2024 |website=[[Science Friday]] |language=}}</ref>

The first known mention of the myth in modern print was in the 1995 novel ''Wanted: Rowing Coach'' as a "twenty-second rule".<ref>{{Cite OED|term=second|id=7821975804|access-date=July 10, 2024}}</ref>

== Research ==
The five-second rule has received some scholarly attention.<ref>{{Cite news |last=Deardorff |first=Julie |date=August 9, 2010 |title=Capsule: The five-second rule |url=https://www.latimes.com/archives/la-xpm-2010-aug-09-la-he-capsule-20100809-story.html |access-date=July 10, 2024 |work=[[Los Angeles Times]]}}</ref> It has been studied as both a [[public health]] recommendation and a [[sociological]] effect.

=== University of Illinois ===
In 2003, Jillian Clarke, a high school student in an apprenticeship, investigated the rule. She found 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 ''[[Escherichia coli|E. coli]]''. On the other hand, Clarke found no significant evidence of contamination on public flooring.<ref name="aces">{{cite news |last= |first= |date=September 2, 2009 |title=If You Drop It, Should You Eat It? Scientists Weigh In on the 5-Second Rule |url=http://news.aces.illinois.edu/news/if-you-drop-it-should-you-eat-it-scientists-weigh-5-second-rule |url-status=dead |archive-url=https://web.archive.org/web/20130727132440/http://news.aces.illinois.edu/news/if-you-drop-it-should-you-eat-it-scientists-weigh-5-second-rule |archive-date=July 27, 2013 |access-date= |work= |publisher=[[University of Illinois College of Agricultural, Consumer, and Environmental Sciences]]}}</ref> For this work, Clarke received the 2004 [[Ig Nobel Prize]] in public health.<ref>{{cite web |title=Winners of the Ig® Nobel Prize |url=http://improbable.com/ig/ig-pastwinners.html#ig2004 |url-status=live |archive-url=https://web.archive.org/web/20090830181439/http://improbable.com/ig/ig-pastwinners.html#ig2004 |archive-date=August 30, 2009 |access-date=July 10, 2024 |website= |publisher=[[Ig Nobel Prize]]}}</ref>

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.<ref name=":0">{{cite journal |author=Dawson |first1=P |last2=Han |first2=I |last3=Cox |first3=M |last4=Black |first4=C |last5=Simmons |first5=L |date=1 April 2007 |title=Residence time and food contact time effects on transfer of Salmonella Typhimurium from tile, wood and carpet: testing the five-second rule |journal=[[Journal of Applied Microbiology]] |volume=102 |issue=4 |pages=945–953 |doi=10.1111/j.1365-2672.2006.03171.x |pmid=17381737 |s2cid=19871846 |doi-access=}}</ref> Tested on surfaces that had been contaminated with salmonella eight hours previously, the bacteria could still contaminate bread and [[Bologna sausage|baloney]] lunchmeat in under five seconds. But a minute-long contact increased contamination about tenfold (especially on tile and carpet surfaces).<ref name="bologna">{{cite news |last=McGee |first=Harold |author-link=Harold McGee |date=May 9, 2007 |title=The Five-second Rule Explored, or: How Dirty Is That Bologna? |url=https://www.nytimes.com/2007/05/09/dining/09curi.html |url-access=subscription |access-date=July 10, 2024 |work=[[The New York Times]]}}</ref>

=== Rutgers University ===
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 {{convert|5|in|cm|spell=in}} 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."<ref>{{Cite news |last=Guarino |first=Ben |date=September 13, 2016 |title=The 'five-second rule' for eating food? Scientists just demonstrated how gross it is. |url=https://www.washingtonpost.com/news/morning-mix/wp/2016/09/13/the-five-second-rule-for-eating-food-scientists-just-demonstrated-how-gross-it-is/ |access-date=July 10, 2024 |newspaper=[[The Washington Post]]}}</ref>

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.<ref>{{Cite web |last=Carroll |first=Aaron E. |author-link=Aaron Carroll |date=October 10, 2016 |title=I'm a Doctor. If I Drop Food on the Kitchen Floor, I Still Eat It. |url=https://www.nytimes.com/2016/10/11/upshot/im-a-doctor-if-i-drop-food-on-the-kitchen-floor-i-still-eat-it.html |archive-url=https://web.archive.org/web/20161010110551/https://www.nytimes.com/2016/10/11/upshot/im-a-doctor-if-i-drop-food-on-the-kitchen-floor-i-still-eat-it.html |archive-date=October 10, 2016 |access-date=July 10, 2024 |website=[[The Upshot]] |publisher=[[The New York Times]]}}</ref>

===Other===
A 2014 study by biology students at [[Aston University]] in England suggested that there may be a basis for the five-second rule.<ref>{{cite web|url=https://www2.aston.ac.uk/news/releases/2014/march/five-second-food-rule-does-exist/index.aspx|title=Researchers prove the five-second rule is real|website=Aston University}}</ref> 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.<ref>{{cite news|url=https://www.independent.co.uk/news/science/five-second-rule-food-dropped-floor-germs-scientists-professor-anthony-hilton-aston-university-a7629391.html|title='Five-second rule' for food dropped on the floor approved by germ scientists|author=Ryan Hooper|date=March 15, 2017|access-date=March 15, 2017|publisher=The Independent (UK)}}</ref> 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.<ref>{{Cite web |last=Greenemeier |first=Larry |title=Fact or Fiction?: The 5-Second Rule for Dropped Food |url=https://www.scientificamerican.com/article/fact-or-fiction-the-5-second-rule-for-dropped-food/ |access-date=2023-05-02 |website=Scientific American |language=en}}</ref>

===Informal===
The five-second rule was featured in an [[MythBusters (2005 season)#Five-second Rule|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.<ref>{{cite web |last=Conley |first=Ken |date=October 2005 |title=Annotated Mythbusters: Episode 39 Chinese Invasion Alarm, 5 Second Rule |url=http://kwc.org/mythbusters/2005/10/mythbusters_chinese_invasion_a.html |url-status=dead |archive-url=https://web.archive.org/web/20080321030933/http://kwc.org/mythbusters/2005/10/mythbusters_chinese_invasion_a.html |archive-date=March 21, 2008 |access-date=}}</ref>{{Unreliable source?|date=July 2024}} An episode of ''[[Food Detectives]]'' found that bacteria will cling to food immediately.<ref>{{Cite news |last=Hale |first=Mike |date=2008-08-05 |title=Private Eye for the Food Guy: Cuisine Sleuths on the Case |url=https://www.nytimes.com/2008/08/05/arts/television/05food.html |access-date=2025-04-26 |work=The New York Times |language=en-US |issn=0362-4331}}</ref>

== References ==
{{Reflist}}

{{portalbar|Food}}

[[Category:American cultural conventions]]
[[Category:Food safety]]
[[Category:Misconceptions]]
[[Category:Rules of thumb]]
[[Category:Applied microbiology]]
[[Category:Urban legends]]
[[Category:Pseudoscience]]