“The "five-second rule" — the belief that food dropped on the floor is safe to eat if picked up within five seconds — prevents the transfer of harmful bacteria to food.”

This study aims to determine the bacterial transfer rate on different produce types when dropped for various contact times onto floor surfaces contaminated with Listeria monocytogenes. Results showed that transfer from all produce types occurred from both the carpet (10.56%) and tile (3.65%) surfaces. Still, percent transfer was not statistically significant among different times used in this study (P > 0.05).

Experiments they reported in the journal Applied and Environmental Microbiology in 2016 showed that the five-second rule is really no rule at all. They found that the longer food sat on a bacteria-coated surface, the more bacteria glommed onto it—but plenty of bacteria was picked up as soon as the food hit the ground. The bigger culprit here is not time but moisture. Wet food (watermelon in this case) picked up more bacteria than drier food, like bread or gummy candy.

Rutgers researchers have disproven the widely accepted notion that it's okay to scoop up food and eat it within a “safe” five-second window. Donald Schaffner, professor and extension specialist in food science, found that moisture, type of surface and contact time all contribute to cross-contamination. In some instances, the transfer begins in less than one second.

Many cling to the “five-second rule,” which asserts that, if you pick up dropped food within five seconds of dropping it, it is safe to still eat. However, University of Alabama at Birmingham researchers have debunked this myth, explaining that bacteria transfer can occur immediately upon contact. “Bacteria can transfer to food the moment it touches a surface,” said Jessica Scoffield, Ph.D., associate professor in the UAB Department of Microbiology.

Researchers at Rutgers University say they have 'disproven' the notion that it's OK to eat food that's fallen on the floor within five seconds. Donald Schaffner, a professor and extension specialist in food science at Rutgers, found that food could be contaminated in less than a second by moisture, type of surface and contact time. 'The 'five-second rule' is a significant oversimplification of what actually happens when bacteria transfer from a surface to food. Bacteria can contaminate instantaneously.'

Although this research shows that the five-second rule is “real” in the sense that longer contact time resulted in more transfer, it also shows that other factors, including the nature of the food and the surface, are of equal or greater importance. The five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food.

By analyzing bacterial transfer at <1, 5, 30, and 300 seconds, they found that longer contact times resulted in more transfer but some transfer took place “instantaneously,” after less than 1 second, thus debunking the five-second rule once and for all. 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 2016 Rutgers University study found that the transfer can happen in milliseconds, not seconds. ... And according to the CDC, some bacteria can linger on surfaces for hours or even days.

The five-second rule effectively has no basis in reality, per Popular Science: In 2003, a Chicago student determined that bacteria transfers to food “very quickly.” In 2006, food scientists at Clemson University found that a contaminated tile transferred 99% of its bacteria to a piece of bologna after just five seconds. Ergo, even five seconds won't save you.

Research has shown that bacteria can transfer to food almost instantaneously upon contact with a contaminated surface. The type of food and the surface it falls on both play significant roles in this process. For instance, moist foods tend to pick up more bacteria compared to dry ones, and surfaces with higher levels of bacteria will contaminate food faster.

Rutgers University researchers found that bacteria may transfer to food that has fallen on the floor no matter how fast you pick it up. Food science professor Donald Schaffner found that cross-contamination can occur in less than one second, dependent upon certain conditions--moisture level, surface time and contact time. Overall, the oversimplified concept of 5-second rule has been overshadowed by the fact that the nature of the food and the surface it falls on are of greater importance. Bacteria can transfer from surface to food instantly.

Researchers at Aston University in Birmingham, England, now suggest that the five-second rule is indeed true. But a 2007 study of the five-second rule from Clemson University in South Carolina argues that there is no safe window for dropped food. Their data points to a "zero-second rule." Both the Aston study and the Clemson study used nearly identical methods of investigation, and ultimately had the same results—but with staggeringly different conclusions.

Bacterial transfer can occur almost instantaneously when food touches a contaminated surface (such as the floor), and various factors such as surface type, food moisture, and environmental cleanliness play critical roles in this process.

The 2016 study did find that spending more time on the floor resulted in higher bacteria transfer rates. “Bacteria particles take time to travel and to collect at a high enough concentration to make you sick,” says Dr. Zuberi. “In less than five seconds, you're less likely to reach that level of contamination.” That said, the study did also find that certain foods (again, the wetter, more absorbent ones) collected some bacteria immediately upon hitting the floor.

The 'five second rule' about picking up food after it has been dropped on the floor may have some scientific basis, according to research. Aston University researchers looked at two pathogens from three indoor floor types and transfer to toast, pasta, biscuit and a sticky sweet when contact was made from three to 30 seconds.

The "five-second rule" is a popular belief that if food is dropped on the floor and picked up within five seconds, it's still safe to eat because it hasn't had enough time to get contaminated by bacteria. However, scientific research generally contradicts this claim, suggesting that the rule is more myth than fact. Studies have shown that bacteria can transfer to food almost immediately upon contact with a contaminated surface.

In experiments carried out at the same university, lollies were dropped on a floor that was coated in E. coli. In all cases, the harmful bacteria took less than five seconds to transfer to the lollies. In another experiment Professor Paul Dawson, of Clemson University South Carolina, contaminated different surfaces with Salmonella typhimurium... Professor Dawson found that more than 99 percent of the salmonella transferred to food dropped on the tiles in less than five seconds.

What's surprising is it didn't matter whether they left the bologna for five seconds or sixty seconds, the same amount of bacteria was transferred. ... This debunks the myth of the five second rule because within five seconds, bacterial transfer has already occurred.

Unfortunately, researchers have now proven that the 'five second rule' for eating food off the floor is, in fact, not scientifically accurate. The time it takes bacteria to transfer onto food can actually be less than one second, according to researchers at Rutgers University led by professor Donald Schaffner. Their first findings confirmed that moisture, surface type and the fabled contact time all have a part to play in cross contamination.

Earlier studies, such as a 2003 experiment by ABC News' MythBusters and a 2007 University of Illinois study, suggested limited bacterial transfer under specific conditions like dry surfaces, providing some weak support for minimal risk in under 5 seconds, but these were less rigorous than the Rutgers peer-reviewed work.