The Five-Second Rule: Fact or Fiction? | Almanac.com

The Five-Second Rule: Fact or Fiction?

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How true is the 5 second rule?

The Editors
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We’ve all done it: Yelled “5-second rule!” after dropping food on the floor, then quickly picked it up and popped it into our mouths. The as­sumption is that 5 seconds is not a long enough time for the food to pick up harmful bacteria. Or is it?

Testing the 5-Second Rule

A high school student doing an apprenticeship in a University of Illinois laboratory decided to test the validity of the 5-second rule. She took swab samples from floors around campus to determine bacteria counts. The floors were surprisingly clean.

Next, she inoculated rough and smooth floor tiles with E. coli bacteria. She placed gummy bears and fudge-stripe cookies on the inoculated tiles for 5 seconds, then examined the foods under a high-power microscope.


Her findings showed that in all cases, E. coli was transferred from the tile to the food, demon­strating that microorganisms can move from ceramic tile to food in 5 seconds or less. Clarke found that more E. coli was transferred from smooth tiles than from rough tiles and that both the dry cookies and the gummy bears be­came contaminated from only 5 seconds of con­tact with the inoculated tiles.


So, the next time some yummy morsel falls to the floor, resist the temptation to pick it up quickly and eat it. We know it’s hard, but just trash it.

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