You’ve probably heard about the five second rule.

If food falls from your plate onto the floor, as long as you pick it up before five seconds, allegedly it’s okay to put it back on your plate and eat it – five seconds is not enough time for germ transfer.

Now for reality. The above is largely inaccurate. Years back, a high school senior, Jillian Clarke, had a six-week internship at the University of Illinois at Urbana-Champaign, in the food science and nutrition department. She scientifically studied the matter under the microscope. Her finding: On clean floors with dry food, there is slight germ transfer. On less clean floors and not dry food, watch out!

Germs Move Fast

To understand how quickly germ transfer occurs, imagine that you’re about to bite into a juicy Swedish meatball. As luck has it, the meatball falls off of your plate and onto the shag carpet underneath your feet. It’s easy to understand that if a juicy meatball comes in contact with the shag carpet, the germ transfer is instantaneous. As such, after you pick up that meatball, you won’t want to insert it into your mouth.

In a crowded train station, suppose you drop your unwrapped Snickers bar on the floor. Are you still going to eat it? Possibly, if it landed flat with a thud, and you can adroitly scrape off the side that touched the floor. What if it rolled along the floor? You might moan and groan, but you’re not going to put that candy bar in your mouth!

Quick Draw McGraw – The same holds true for any food. Suppose you drop a cracker on a tile floor. Your reflexes are lightning fast and you pick it up in a second. Have you minimized the germ transfer? A bit, but some transfer is instantaneous.

Even when you pick up a fallen food item in less than a second, once it hits the floor, well... Do you want to be safe?

When Not to Discard Food

Are there “exceptions”? At home, you are more in control than elsewhere. When you’ve recently cleaned your floor and you’re not a germaphobe, an item such as a cracker is probably okay to put back on your plate, once dusted off. If you drop a piece of celery, same thing. You could rinse it under the faucet and if you subsequently eat it, you’ll live to tell about it. Drop that Swedish meatball, even on your recently cleaned floor... and well, let’s simply say I wouldn’t eat it.

What other exceptions could there be? When you drop a pistachio peanut, still in the shell, it’s reasonably okay to pick it up, crack open the shell, and down it. A peanut butter sandwich, face down? No way! A peanut butter sandwich face up? Possibly. You could always take a serrated knife and scrape off the underside of the bread that touches the floor. Once again, you’ll be reasonably okay.

On the road, when your food hits the floor, don’t think twice. Chuck it.