Is the 5 Second Rule True?

The ‘Five Second Rule’ is a rule that many people grew up following. It is the idea that if one drops food on the ground it is still safe to eat if it is picked up within five seconds of dropping it because there would not have been enough time for bacteria to transfer on to the food. Researchers at Rutgers have investigated the validity of this rule.

Should you follow the 5 second rule?

Should you follow the 5 second rule?

The researchers investigated the Five Second Rule by using four types of food (watermelon, bread, bread and butter, and gummy candy) dropped on four different surfaces (stainless steel, tile, wood, and carpet). According to the study, they used the bacteria Enterobacter aerogenes.It does not cause disease but is closely related to Salmonella. The study also varied the amount of time that the food was dropped on the surface. The varied times were one second, five seconds, 30 seconds, and 300 seconds.

Donald Schaffner, the conductor of the experiment, cites moisture as one of the factors that most affected the transfer of bacteria from the different surfaces on to the different foods. This is seen in watermelon, which had the highest amount of bacteria transfer, and gummy candy, which had the lowest amount of bacteria transfer. Why is this? Bacteria move with the help of flagella or pilli. Flagella is a long tail structure that moves around to propel the bacteria and pilli cover the bacteria and pull the bacteria forward. The presence of moisture aids the movement of bacteria. Another factor was the length of contact, the longer the food was left on the surface the more contaminated it was with bacteria. The surface that the food ‘fell’ on in the experiment was another factor that affected amount of bacteria. According to Schaffner, carpet had a lower amount of bacteria transferred then tile and stainless steel, and wood varied.


Flagella, one method that bacteria uses in order to move.

The results of this study are based off of 20 trials of 128 scenarios. In class, we learned that not all data is equal. Data has a stronger inference when it is a properly designed experiment and has an even stronger inference when it is a good experiment with good field observation or evidence of mechanism. This experiment has strong inference because there are multiple trials. Since there are multiple trials, if they all yield similar results this proves the validity of the outcomes. This experiment had 20 trials making the results of the experiment valid as it was a fairly designed experiment. The repeat of trials helps reduce random chance, although it is always still a factor.

I know that I drop food all of the time and then debate whether it is safe to eat or not. This article proves that depending on the food or surface your food may be safe to eat if it is picked up in a short amount of time. However, if your food has moisture and has fallen on carpet or stainless steel- it is safer to not eat the food. If it is a gummy candy falling on a carpet- it is pretty safe to eat. However, this experiment makes me think about the number of bacteria that can be on your food when you drop it. Five second rule or not- its always better to be safe than sorry with food poisoning.

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For more information on how bacteria move click here.

3 thoughts on “Is the 5 Second Rule True?

  1. Victor William Gregory

    This blog post just made me exponentially more paranoid. I am already one who does not believe in the 5 second rule, meaning I won’t eat food off the floor. Now that I know which types of surfaces are more prone to transferring bacteria, I will probably end up hyper-analyzing every situation that involves the consumption of food now. I find it interesting that something like a gummy candy is likely to pick up bacteria as quickly. I would have assumed it was the opposite. This was really compelling and I wouldn’t have thought to write about it.

  2. Jessica Heckler

    As a firm believer in the 5 second rule, this article brings a lot of concern to my attention about how many things I quick picked up off the ground, gave it a look, and decided it was probably still okay to eat. I know some of you are reading this and thinking I’m gross, but I know you have all been there. Whether its the last bite of your favorite candy bar or food too good to let go to waste, lets all admit that we have been guilty of following this rule at some point or another in our lives. However, this article seriously makes me reconsider every piece of food I have ever eaten after it has touched a questionable surface. I had no idea that bacteria could really travel that fast from one surface to another. I will definitely not be eating anything off of tile or stainless still anytime soon, and generally I never would have eaten anything off of a carpet anyways because I was afraid of carpet fuzz on my food. I guess my days of living by the five second rule are over..

    After reading this though, I decided to a little bit of my own research, realizing that if it hasn’t hurt me yet, will it ever? This view point is of this article is quite similar to mine. It reminds us that bacteria is on other surfaces besides the floor. There very well may be more harmful bacteria on the kitchen counter if it has not been cleaned properly than the floor, but we still eat things that we prepared on the counter! After reading that article, I have decided that, even though your blog and reading about the spread of bacteria from one surface to another is quite eye opening, I will probably still eat the last bite of my favorite candy bar if I so happen to drop it on the floor and the 5 second rule applies.

    1. Katherine Yuen

      I’ve never been one to follow the five second rule since I’m pretty paranoid about getting sick, but I’m glad you brought this up! Although it does make me wonder how much we should really worry about the issue of getting germs on our food. I know that a lot of people don’t wash their hands before every meal, even if it’s something they eat with their hands. If I’m touching a chair or a table or a doorknob with tons of germs on it, and then touching my food, is that the same as rubbing my food all over the chair, table, or doorknob for 1 second? I couldn’t find the exact answer to my question (although if you know, please tell me because now I’m worried about germs), but I did find Make this article which discusses a study of about 300 people that found that our hands are pretty nasty and bacteria-covered, but only 12% of us wash our hands before eating! If you’re ever looking for me, you can find me at the nearest sink, washing my bacteria ridden hands.

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