The Truth Behind the 5-Second Rule

You drop your food on the floor and quickly snatch it up. “It’s okay to eat,” you exclaim, “5 second rule!” As you salvage that coveted food off the floor, you promptly pop it in your mouth before anyone can scrunch up their face in horror.

Many people refer to this as the 5-second rule. The idea behind it is that if food is only on the floor for five seconds or less, it’s still safe to eat. But is that true?

That may depend on what the food is, where it lands and who you ask.

Consider this: There are microorganisms and bacteria just about everywhere. Some bacteria, such as E. coli, salmonella or listeria, can cause you to get sick. The Centers for Disease Control (CDC) estimates there are over 9 million cases of foodborne illnesses each year in the U.S. and cross-contamination is partially to blame. But just because most surfaces contain some type of bacteria, it doesn’t mean you’ll automatically get sick if your food touches it.

A study published in 2016 by the American Society for Microbiology challenged the parameters of the 5-second rule. The study tested cross-contamination between household surfaces and food using scenarios that differed by surface type, food type and the amount of time food was in contact with contaminated surfaces. The study showed that the longer the contact time, the more likelihood of cross-contamination.

But the study also showed that there is no magical number before which cross-contamination occurs. Although time increases the likelihood of bacteria transfer, some cross-contamination takes place instantly. So although food that drops for under 5 seconds is less likely to be contaminated, it’s not a guarantee that it’s free from bacteria.

The research also showed that the nature of the surface and the food were of equal or greater importance when it came to how much bacteria wound up on the food. Surfaces that are non-porous, such as tile, were shown to transfer bacteria more easily than porous surface such as carpet or wood. Dry surfaces may be less likely to harbor bacteria that can cause foodborne illnesses because most microorganisms can’t survive without moisture. But that doesn’t mean there’s no hair, dust, pet dander or whatever comes off of the soles of your shoes.

The type of food also factors into the equation. Food that is wet or sticky is more likely to pick up bacteria or dirt than food that is dry. There’s a difference between dropping a chunk of watermelon and a dry cracker on the floor when it comes to what sticks to it.

Despite the few studies done that have about the transfer of bacteria from surfaces to food, there is still no real consensus on how safe it is to eat food off the floor. But if you want to err on the side of caution, throw out any food that hits the ground, even if it sits there for 5 seconds or less. After all, isn’t it better to be safe than sorry?