From the kitchen scientist, Harold McGee, on the 5 (or was it 7?) second rule; you know, drop food, pick it up quick and then it’s still “safe”:
‘It’s not surprising that food dropped onto bacteria would collect some bacteria. But how many? Does it collect more as the seconds tick by? Enough to make you sick?
The infectious dose, the smallest number of bacteria that can actually cause illness, is as few as 10 for some salmonellas, fewer than 100 for the deadly strain of E. coli.
Of course we can never know for sure how many harmful microbes there are on any surface. But we know enough now to formulate the five-second rule, version 2.0: If you drop a piece of food, pick it up quickly, take five seconds to recall that just a few bacteria can make you sick, then take a few more to think about where you dropped it and whether or not it’s worth eating.’
(Just in case you need something else to get hysterical about).