MICROBIOLOGIST PUTS FIVE SECOND RULE TO THE TEST

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Microbiologist Puts the 5-Second Rule to the Test — How Long Is Too Long to Eat Off the Floor?

“I thought it would be fun for people to know all the little nastiness that we don’t think about every day,” Chicago microbiologist Nicholas Aicher said

By Vanessa Etienne  Published on April 15, 2025 03:19PM EDT

 

Almost everyone has dropped food on the floor and was immediately filled with disappointment because they still wanted to eat it. The moment is often met with someone nearby yelling, “Five-second rule!”

 

The so-called rule claims that food is still safe to eat if it’s been on the floor for five seconds or less. Now, a Chicago microbiologist is going viral for putting the old school rule to the test.

 

Nicholas Aicher, a senior quality control analyst, is known for making TikTok videos where he swabs public surfaces like gas station pumps, fitting rooms, TSA bins, beauty testers and movie theater seats to test them for bacteria. His account — @howdirtyis — has garnered more than 11 million likes.

 

“I thought it would be fun for people to know all the little nastiness that we don’t think about every day,” he told Jam Press, according to the New York Post.

 

In January, Aicher was asked by one of his followers to test the five-second rule. So he did.

 

In the clip, he placed a petri dish on the ground for specific times, ranging from zero seconds to one minute. After incubating the samples in a cultivator, he revealed which ones had evidence of microbial growth.

 

The results revealed that every single sample had white bacterial spots.

 

“Looks like even zero seconds is too long,” the scientist wrote in the clip while showing the petri dishes. Aicher also noted that the one-minute sample had about the same amount of bacteria as the five-second sample.

 

In the comments, followers were shocked by the results.

 

“Never eating food from the floor again…” one person wrote. Another added, “Nooooo i LIVE by the 5 second rule! 😫😫😫.”

 

However, some viewers weren't convinced by the results and even claimed the test needs a “control” sample to be accurate.

 

“I'll pretend I didn't see this so I can keep blissfully doing the 5 second rule,” one user wrote, while another quipped, “Meh. I was doing the 5 second rule throughout my childhood and I'm still healthy.”

 

“Need a control. One that doesn’t touch the floor but is opened to air and then closed,” another commenter chimed in.

AH: How do you do anything for zero seconds?