Everyone knows that you have 5-seconds to pick up food that has dropped on the floor and it will still be good. After all, how quickly do bacteria go, “Hey guys, look at that! Food on the floor. Let's go!!”

Turns out, pretty quickly. Bacteria can be fast!

In 2003, Jillian Clarke, a senior at the Chicago High School for Agricultural Sciences in Illinois, put the five-second rule to the test. She inoculated two types of tiles—smooth and rough—with Escherichia coli and dropped gummy bears and cookies on the tiles for five seconds. Clarke and her coworkers saw that bacteria transferred to food very quickly, even in just five seconds, thus challenging the popular belief.

A few years later, food scientist Paul Dawson and his students at Clemson University in South Carolina also tested the five-second rule and published their results in the Journal of Applied Microbiology. When they dropped bologna sausage onto a piece of tile contaminated with Salmonella typhimurium, over 99% of the bacteria transferred from the tile to the bologna after just five seconds. The five-second rule was just baloney, Dawson concluded.

Your chance of falling ill after eating food that has touched the floor depends on factors like how contaminated the floor is and the type of bacteria present. “Based on our studies, the kitchen floor is one of the germiest spots in the house,” Charles P. Gerba, a microbiologist and professor of virology at the University of Arizona, tells Popular Science. Believe it or not, “the kitchen is actually germier than the restroom in the home,” he added. This is because, compared to other rooms in a house, the kitchen gets a lot of foot traffic and food debris often falls on the floor, creating an ideal breeding ground for bacteria. While most of the bacteria lurking on kitchen floors are harmless, some—like Clostridium, Campylobacter, Salmonella, and Escherichia—can cause food poisoning.

If you just hate throwing away food, there are safer options than relying on the five-second rule. Rinsing dropped food can reduce contamination—although this method isn’t foolproof. “Rinsing is a good idea if it is a fruit or vegetable, but it’s harder to rinse off microbes from meat due to their rougher surface,” Gerba said. “You should also rinse food off if it falls in the kitchen sink as it is also very germy because of the moisture in the sink,” he suggested.

The next time you’re tempted to eat that cookie you just dropped, remember: bacteria move fast. As hungry as you may be, do you really want to eat a Salmonella-laced cookie?