No, no, smart people argue, the five-second rule is a fallacy — like slapping a hand on a red-hot stove, if you drop food on the ground, time is relevant. It’s been Mythbusted, and there’s a Snopes entry that reports, "Status: False." Well, the experts are suckers, maybe: A microbiologist and his students at the U.K.’s Aston University dropped all kinds of British things onto floors — toast, pasta, biscuits, "a sticky sweet" — then set out to measure the transfer of bacteria like E. coli and the talented Mr. Staphylococcus. (Hats off to that janitorial staff, by the way.) They report it’s "fine to eat food that has only had contact with the floor for five seconds or less."
Sure, there are caveats. This isn’t a peer-reviewed letter to Nature, after all, and researcher Anthony Hilton adds that consuming any dropped food "carries an infection risk." Also, it definitely depends on "which bacteria are present" and whether it’s a carpet, tile, or laminate floor.
To this we should add it’s probably not helpful if the floor in question is located in a cave where cooked beans fester at room temperature, vampire bats hang from the ceiling, and little kids bounce around all over the place picking their noses. Still, if you’re really just looking for an excuse to eat that thing that just fell on the floor, just tell yourself that carpet "actually pos[es] the lowest risk," then maybe leave everything else up to fate.
Researchers Prove the Five Second Rule is Real [Aston University]