What Science Has to Say About the 5-Second Rule

I like to imagine that germs on the floor hold their breath and count to five before hopping on any dropped food, but some scientists paint a different picture of what's actually happening under the microscope.

One study found results that led scientists to adhere to a zero-second rule (or no-tolerance policy) where there is no safe window to consume food after it has fallen on the ground. These researchers found that salmonella and other bacteria can live up to four weeks on dry surfaces and can be transferred to food as soon as it hits the floor. That means that germs on the floor can be lurking for a month just waiting for food to drop.

However, a more recent study found that food picked up quickly is less likely to contain bacteria than food left on the floor for longer periods of time. In addition to the time lapsed, this study found that bacteria are more likely to transfer from laminate or tiled surfaces than from a carpeted floor. Researchers also found evidence that certain foods are less likely to collect bacteria in five seconds than others; dry foods like cookies and chips don't settle or stick to surfaces the same way that cooked pasta and sticky candy do. So, given these findings, if you have a handful of crackers that hit the floor when you're sitting on the couch, you're safer eating those than a few noodles that touched your kitchen floor.

Anyone who has suffered from foodborne illness can tell you that contaminated food is no laughing matter, but being anxious about germs 24/7 is not a healthy habit we're trying to promote. So, is the five-second rule OK to follow? The short answer is: sometimes. Follow it on a case-by-case basis depending on your environment and the food you're eating. But if you're wavering back and forth, do your body (and brain) a favor and just toss it.