Science Is Calling BS on the 5-Second Rule

A large majority of us grew up believing the magical “five-second rule,” where if you grab food you’ve dropped on the floor, it doesn’t pick up any germs if you retrieve it quickly. And now that some of us are parents, the same mantra still applies. Dropped your sticky lollipop? No worries, five-second rule!

You didn’t really believe that was true, did you?

Researchers at Rutgers University in New Jersey have revealed that bacteria can contaminate food that falls on the floor in less than a second.

The scientists tested four surfaces — stainless steel, ceramic tile, wood, and carpet; and four different foods — watermelon, bread, bread and butter, and gummy sweets.

They also looked at four different contact times — less than one second, five, 30, and 300 seconds — and measured bacteria contamination for each.

Watermelon had the most contamination, while gummy sweets had the least, suggesting that transfer of bacteria from surfaces to food is affected most by moisture. Carpet also fared better when it came to contamination transfer than tile or stainless steel.

Though it is fair to say that the longer the food stays in contact with the surface, the more bacteria will transfer, what isn’t true is that nothing happens under five seconds. Other factors, including the type of food and the surface it falls on, are of equal or greater importance.

“The popular notion of the ‘five-second rule’ is that food dropped on the floor but picked up quickly is safe to eat because bacteria need time to transfer,” explains lead researcher Donald Schaffner, professor and extension specialist in food science at Rutgers.

“We decided to look into this because the practice is so widespread. The topic might appear ‘light,’ but we wanted our results backed by solid science.”

“The ‘five-second rule’ is a significant oversimplification of what actually happens when bacteria transfer from a surface to food. Bacteria can contaminate instantaneously,” he continues.

So next time you drop candy on the floor, though it’s totally crushing, you should probably just cut your losses and toss it in the trash, unless of course it was only on the floor for, like, a second. The one-second rule is totally a thing, right?

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