Most people know the “five-second rule”: the idea that if food that’s fallen on the floor has been there less than five seconds, it’s still acceptable to eat. No one knows the origins of this questionable rule — and plenty of people think it’s kind of gross — but that hasn’t stopped anyone from picking up a dropped Oreo and shouting “five-second rule!” before.
Actual scientists have devoted time and resources to testing the five-second rule. And surprisingly, it’s not an entirely bogus theory — depending on the cleanliness of the floor. To be clear, no scientist has gone on record recommending that you eat dropped food. However, a science experiment conducted at the University of Illinois Urbana-Champaign proved that as long as the food was picked up within the five-second time limit, the presence of microorganisms on the dropped food was minimal. However, the experiment was conducted after first sanitizing the flooring, and it only applied to hard flooring like tile and wood, which are less likely to serve as an incubator for pathogens. No testing was conducted on carpeting and other soft surfaces, which can hold moisture and become breeding grounds for bacteria. In any case, it’s definitely not recommended to blindly follow the five-second rule. You have no way of knowing which pathogens are on your floor, so unless you regularly disinfect, it’s best to play it safe and follow another rule: When in doubt, toss it out.