The Five-Second Rule: Fact or Fiction?

How true is the 5 second rule?

November 23, 2020
Five Second Rule

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.


The 2011 Old Farmer's Almanac

Reader Comments

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Five Second Rule

Got to love Hudson's reasoning below.
Thanks for the laugh !

Five second rule

Five second rule does not matter if you have a three second dog!

5 Seconds

I don't care, if it's an Oreo I'm eating it. Mind you, I'm not scraping up mashed potatoes.......


A first for me! Never have heard of this until reading this article. Since I can remember, any food dropped on the floor is tossed into the trash! Never, never eaten no matter how clean the floor is or what type of flooring. I wonder - how and why would anyone want to eat something that has been on the floor!! Should a dish cloth be dropped, it goes in the washing machine. And --- NO --- I am not an overly clear nor an overly dirty house keeper, just using common sense,

5 second rule.

Just use common sense! I drop grapes or berries on the floor from time to time but after picking them up I wash them off and eat them. I have done this for over 60 year's and I have never gotten sick.
Now, if you drop your gum in the chicken house or your peanut butter and jelly sandwich falls face down in the outhouse just let it go!!

Questionable Experiment

I have seen this type of experiment done several times before by scientists. They always use untreated surfaces using only the microorganisms already present (such as a kitchen floor or a public sidewalk), or they use the types of microorganisms you would most likely find on the surfaces, in the amounts that would be there in real life situations. They all stated that the amount of time time food is in contact with the surface does indeed affect how many germs get on the food. They also stated that all contact which was 5 second or shorter was not long enough for harmful amounts to be transferred, although longer exposure or repeated consumption of contaminated food in a short amount of time could lead to a build-up of harmful amounts. Even on a sidewalk which was found to contain Salmonella & E-Coli, there was not enough of either within the 5 second exposure to cause any harm or illness to a normally healthy person. I don't feel the experiment in this article is valid since we don't know how much was used to contaminate the area, which could have been more than what would be there in real life situations, and we don't know how much was transferred to the food or if any measurements were even taken. The whole thing seems unscientific and poorly executed.

It isn't that simple.

To expand on a previous comment: "contamination" is relative. NOTHING we eat is sterile in a microbiological sense; the key is to keep things reasonably clean. Our immune system is designed to handle small quantities of bacteria (and many viruses), and such exposure is probably beneficial and necessary, particularly in childhood; illness occurs when the dose gets too high. People with weakened immune systems - AIDS, some cancer patients on chemo, transplant patients on immunosuppression - have a lower threshold for illness, and may need to be more careful; healthy folk can afford to be a bit more casual.

It also depends on where you are. The countertops in hospitals - the surfaces on which people normally lean, and rest their food - are home to more and worse bacteria than the sidewalks outside, because the widespread (and often necessary) use of antibiotics in hospitals has made many of those bacteria resistant to the usual drugs, and of course because hospitals are where you find the people with the worst infections. You might actually do better eating something off the sidewalk than off of the table in the staff lounge! (Again, dosage is the key: in reality, you're generally safe if you ingest a few microbes.)

Finally, people are their own little ecosystems; the average person is home to about a thousand species of bacteria! (A disturbing thought, perhaps, but the vast majority are beneficial or harmless.) If you drop something on the floor of your own house, the bacteria with which it will come into contact are mostly the ones you already harbor; it's generally exposure to NEW microbes which makes people sick.

Younger generation not eating enough dirt.

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.

5-Second Rule

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.

5 second rule

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!