Five-second rule

The five-second rule is a western food hygiene concept, that states that there is a five second window to pick up food (or sometimes cutlery) after it has been dropped and thus exposed to contamination. Some may truly believe this assertion, whereas most people employ the rule as an amusing social fiction that allows them to eat a dropped piece of food, despite the potential reservations of their peers. The "rule" has been scientifically proven false.

The time of origin of the myth is unclear. Some refer to it as the three-second rule.

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

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. On the other hand, Clarke found no significant evidence of contamination on public flooring. For this work, Clarke received the 2004 Ig Nobel Prize in public health. A more thorough study in 2006 using salmonella on wood, tiles, and nylon carpet, found that the bacteria were able to thrive under dry conditions even after twenty-eight days. Tested after eight hours of exposure, the bacteria was still able to contaminate bread and bologna in under five seconds. But a minute-long contact increased contamination about tenfold (especially tile and carpet surfaces). The researchers at the Rutgers University also debunked this theory by dropping watermelon cubes, Haribo strawberry gummies, plain white bread, and buttered bread from a height of five inches on to the ground. The surfaces selected were slathered in Enterobacter aerogenes. The surfaces used were carpet, ceramic tile, stainless steel and wood. The food was left on the surface in intervals of 5, 30 and 300 seconds. The scientists assessed the amount of E.aerogens transferred between surface and food. Since Bacteria tended to be attracted to moisture, wet food had more risk to have bacteria transferred then dry food. To the surprise of the researchers, carpet transferred fewer bacteria than steel or tile. Wood was hard to pin down. It showed a large variation. The scientists concluded that five-second rule is a “significant oversimplification” for the chance of bacteria to be transferred in real life.

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