From UW Madison News:
If a piece of toast fell on the floor, would you pick it up and eat it? You probably would if you believe in the 5-second rule, which suggests that your spilled breakfast stays germ-free as long as you snatch it up in five seconds.
But while the 5-second rule remains a popular rule of thumb, there is no hard science to support it, says Glenn Chambliss, a bacteriologist at UW-Madison. In fact, if you dropped food in places harboring nasties like E. Coli bacteria, any contamination would happen instantaneously, the scientist says.
At our house we don’t live by “The 5 second rule” for dropped food as much as we do by the “get it before the dog does” rule. And the dog usually wins.