The five-second rule, or sometimes the three-second rule, is a food hygiene urban legend that states a defined time window after which it is not safe to eat food (or sometimes to use cutlery) after it has been dropped on the floor or on the ground and thus exposed to contamination.
There appears to be no scientific consensus on the general applicability of the rule,[1][unreliable medical source?] and its origin is unclear. It is speculated to have originated from legends about Genghis Khan. It was first mentioned in print in 1995.