We’ve all been there. You’re ready to pop that tasty treat into your mouth, and disaster strikes — it hits the floor. You stop and stare for a moment. Assuming your floor isn’t filthy, a small voice says, “Quick, pick it up and eat it!” If it happened in an instant, then maybe you’ll be okay if you do. You might know this as the “five-second rule,” where you can eat something that’s fallen on the floor as long as it hasn’t been sitting there for more than five seconds.

But is this sanitary? Are germs too stunned by the quick intruder to pounce? Or, should you just toss that morsel and get something else to eat?

Where did the five-second rule come from?

Overhead photo of people dining at a table covered in various foods
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No one seems to know the origins of this questionable rule, but the first official usage of it in the media was in 1995 for a Volkswagen commercial. One of the earliest known advocates for eating dropped food dates as far back as the 13th century to Genghis Khan. According to legend, he was known for throwing some pretty extravagant shindigs where food flowed freely. Food was so plentiful that it often fell on the floor, leading to his developing the “Khan Rule.”

The rule stipulated that if any food fell on the floor, it was okay to leave it there for as long as he liked — and that anyone could eat that food no matter how long it had been on the floor. Since the food had been prepared just for him, the ruler refused to believe that anything bad could happen to it just by its being on the floor. Is that sanitary? We don’t think so, but it makes a great origin story.

Great moments in five-second history

Photo of hands removing a pancake from a skillet
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Seven centuries later, a self-taught chef would put the five-second rule to the test on national television. The pioneering television cooking show host Julia Child famously messed up her timing in a pancake flip, and the offending food landed on the stovetop during the potato episode of "The French Chef." Rather than toss it, Julia called out her goof and even encouraged her viewing audience to just pick it up and keep going because “Who is going to see?”

But is that food safe?

Photo of a spilled plate of spaghetti and meatballs on the floor
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Oddly enough, scientists have devoted time and resources to testing the five-second rule. And what’s more surprising is the fact that it’s not an entirely bogus theory — depending on the cleanliness of the floor.

To be clear, no scientist has gone on record advocating for eating dropped food. However, a science experiment conducted at the University of Illinois Urbana-Champaign proved that as long as the food was picked up within the time limit of the aforementioned rule, the presence of microorganisms on the dropped food was minimal.

However, the experiment was conducted by first sanitizing the flooring before food was dropped, and this applied only to hard flooring like tile and wood, which are less likely to serve as an incubator for pathogens. No testing was conducted on carpeting and other soft surfaces, which can hold moisture and become breeding grounds for bacteria.

So should I eat food off the floor?

Photo of a gloved hand holding a petri dish in front of lettuce
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While you might not have an insane amount of pathogens attach themselves to your food in five seconds, it’s still not recommended to put the Khan Rule to the test. First, you have no idea of which pathogens are on your floor. While their presence on a dropped chip might be minimal as compared to eating raw or undercooked meat and unwashed veggies, E. coli and salmonella can still make you sick. At best, you can experience a mild case of food poisoning, but on the extreme end, people have died from these infections.

Then no food is safe?

Close up photo of potato chips
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According to the experts, dry foods are slightly safer than wet ones because moisture is a great medium for pathogens to attach themselves. So, a chip might face minimal pathogen transfer whereas an apple or piece of banana might test positive for a higher pathogen count. But we recommend the following advice: when in doubt — throw it out. Just go back to the kitchen and get another snack.