Is the 5-Second Rule Really a Rule?

How long is it safe to leave food that fell on the ground before picking it up and eating it?


Study, Science
Can you eat a cupcake that fell on the floor?

(New Africa /

We’ve all done it. Everyone has, at some point in their life, dropped a cookie on the floor and immediately picked it up, brushed it off, and popped it in their mouth. Most people refer to this as the 5-second rule: a piece of conventional wisdom that states that food that has fallen on the floor is safe to eat if it is picked up within five seconds. But is this true? Now scientists are testing the validity of the wisdom of ages. 

A question of material
The question of the 5-second rule, or in scientific terms, the transfer of bacteria and microorganisms via surface contact, has not often been studied. But a 2016 study in Applied and Environmental Microbiology scientists from Rutgers University have undertaken to test the idea that food is safe to eat if it has fallen on the floor or another contaminated surface if it is picked up quickly enough.

What they found, according to Healthline, is that the 5-second rule, scientifically speaking at least, is pretty much a myth. That’s because bacteria can transfer from one surface to another pretty much on contact. However, the amount of bacteria that is transferred is a factor of time, the amount of moisture in the food, and the surface material. 

In fact, the more moisture in a food, the more bacteria it will pick up. Watermelon, for instance, picked up the most bacteria of all the types of foods tested. In addition, the type of surface the food was in contact with is also a factor. 

Surprisingly enough carpet is relatively safe. It had a much lower transfer rate than wood, tile, or stainless steel. Finally, as common sense dictates, time is also a factor. The longer a piece of food was in contact with a surface the more bacteria it picked up.

Safety first
So is it safe to eat food off the floor? How dangerous is it, really? For the most part, eating a cookie off a clean floor will probably not hurt anyone with a normal immune system, reports National Geographic.

Dr Donald Schaffner,  Department Chair, and Distinguished Professor at Rutgers University, and extension specialist in Food Science, says it really depends on where the food is dropped. He told National Geographic , “If you’re in a hospital and you drop something, you probably don’t want to eat it.” However, “Ninety-nine percent of the time, it’s probably safe.”

Still, according to Healthline, people in at-risk populations, such as children, people who are immuno-compromised and pregnant people should be cautious and probably not eat food off the floor. 

So while the very idea that bacteria doesn’t transfer to food within a few seconds of contact with a given surface is false, the 5-second rule will probably endure. That’s because people really want it to be true and according to Schaffner: “Everybody does this; we all eat food off the floor.”

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