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The Five-Second Rule: Fact or Fiction?

Written By: Heidi Stonehill Executive Editor

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 long enough for the food to pick up harmful bacteria. Or is it?

Testing the 5-Second Rule

A high school student named Jillian Clarke, who was 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, Clarke 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-powered microscope.

e coli bacteria

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.

gummy bears

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.

Amusements

About The Author

Heidi Stonehill

Heidi Stonehill

Executive Editor

Heidi Stonehill is the Executive Editor for The Old Farmer’s Almanac, joining the team in 2001. As such, she manages the content development of the Almanac’s line of wall, engagement, box, and special...

Read more from Heidi Stonehill

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Comments

<span>Randy</span> Wed, 11/28/2018 - 10:51
I too agree with both previous comments concerning the 5 second rule. I wouldn't hesitate to eat something dropped on my home floor, but wouldn't do it in a public place. That being said, I saw a documentary that stated that in years past where ,especially children, would play outside in the dirt that consuming (yes, consuming) foreign substances actually HELP our body's immune system. I don't remember the doc, but it was on Netflix. Summary?? Eat more dirt to be healthy years later in life! To be clear, I'm not talking about eating a mud pie, but as kids, you're naturally going to have dirt wind up in your mouth if you're playing outside. Kids, put down those electronic gadgets (as my grand-kids constantly have in their hands), & get outside & play in good ole "Mother Earth"! She's good for you.
<span>Pipal</span> Sat, 07/16/2016 - 15:36
I have indeed applied the 5-second rule on many occasions in my own residence and, in my 68 years, never gotten ill from it. However, I don't do it in public places, nor do I go around the house inoculating my floors with e-coli, so that could have something to do with it. I've also seen studies that conclude foods with high salt or sugar content are more immune to contamination. In my opinion, a certain amount of contamination keeps our immune systems strong and, therefore, us healthy. I think that hand sanitizers were invented by people with OCD.
<span>Olinda</span> Wed, 11/28/2018 - 10:09
Geez....I thought everyone knew this is just a line when one doesn't want to waste what hit the floor. And I totally agree with the previous comment, I do it at home but would never ever do it in a public place. Gross and no I don't have feces, or e coli smeared on my floors!