Question: If you drop food on the floor, is it safe and hygenic to pick it up and eat it?

Answer: Only if you snatch it up within five seconds.

Or at least that's the conventional wisdom that many of us have lived (and tried not to die) by.

For some reason, most of us happily accept the "five second rule," that popular promise which assures us that it takes five seconds before food that's fallen the ground can become contaminated with bacteria, germs, viruses, and other things with a significant yuck factor.

But guess what: There's no truth behind this claim at all. If you drop food on the floor, it picks up germs. Most of the time, those germs are harmless. But it is possible to pick up all sorts of dangerous bugs, such as E. coli and salmonella.

Much testing -- including two universities and an entire episode on the Discovery Channel's MythBusters -- has been devoted to the subject. They all came to the same conclusion: It takes a lot less than five seconds for germs to transfer themselves from the floor to your food. That doesn't necessarily make eating dropped food dangerous. But don't kid yourself -- if your food just got a whole lot germier.

The rule was originally tested in 2003, when a high school student in Chicago decided to see whether the claim was valid. She dropped gummi bears on a floor laced with E.coli and found that the bacteria immediately contaminated the food. But she also found that, overall, the floors at the University of Illinois which hadn't been doused with E. coli were surprisingly clean and free of dangerous microbes.

Earlier this year, a scientist at Clemson University backed up her findings. He dropped pieces of bread and bologna onto floors that had been contaminated with samonella. They tested a variety of floor surfaces, including wood, tiles, and nylon carpet, and in each case the food picked up the bacteria.

Since I'm not much of a germophobe, I've never worried too much about dropping and then eating, say, a cracker or other dry food. (Sometimes I've waited as long as seven seconds!) But I'm much less likely to do that with food with a higher moisture content, like an orange segment.

Or maybe I'm just like most other people in the study. Most of them were much more likely to pick up a dropped M&M than a broccoli floret.

But then, just because the "five second rule" has been totally discredited, doesn't mean that there can't be exceptions to the rule. Especially if those exceptions are chocolate.