At some time in our lives, most of us have probably invoked the "five-second rule."
A piece of food rolls off your plate and it drops to the floor. It's still safe to eat if it's just there for a few seconds, right? (Especially if nobody saw it!)
This question has inspired several scientific studies over the years. It has also been the subject of TV shows like "Food Detectives" and "MythBusters" (busted!).
Health experts may appreciate the humor. But when it comes to the science behind this bit of wishful thinking, they're all business.
How contaminated the dropped food is depends in part on how contaminated the ground or surface is, and what it's contaminated with, says Melissa Joy Dobbins. She is a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics.
When food drops to the floor or ground, it can pick up bacteria, viruses, parasites, hair, dirt, sand, dead skin or any chemicals that might be on the surface.
"The food may be teeming with bacteria, but it may or may not be foodborne illness-causing bacteria," she says.
Even if it doesn't make you sick, think about what you might be eating.
"Instead of tricking ourselves into thinking it's still a 'clean' piece of food, we should remind ourselves that there are reasons we don't eat off the floor or the ground outside!" she says.
The bottom line is, don't eat food that has been on the ground even for a few seconds.
At Clemson University, Dr. Paul Dawson says the five-second rule still intrigues him after he and his team published a study on it back in 2006.
Dawson admits he got a little caught up in the folklore. "The origin of the five-second rule is sometimes attributed to Genghis Khan, who is reported to have had the 'Khan rule' at banquets for his generals," he says.
"If food fell to the floor, it could stay there as long as Khan allowed and still be eaten," he says. "Because if the food itself was worthy enough to be prepared for Khan, then it would be worthy to eat no matter how long it was on the floor."
There is nothing funny about foodborne illnesses. They can cause vomiting, diarrhea, abdominal pain, fever and chills. Symptoms typically appear suddenly and last a short time. But it's enough time to make you miserable.
Most healthy people don't need medical treatment for food poisoning. But dehydration can result due to fluids lost during your sickness. And certain people need to be especially cautious. Pregnant women, young children, the elderly and those with weakened immune systems are at higher risk for severe infections.
There are two silly but common reactions when we drop food. First, you may look around to see if anyone noticed. "Maybe people think if no one saw it then it didn't really happen -- like if a tree falls in the forest and no one is there to hear it, does it make a sound?" Dobbins says.
Another reaction is to blow on the dropped food, as if that will clean it off. "Not only is it silly, it actually adds 'fuel to the fire,'" Dobbins says."Your mouth contains lots of germs and bacteria, and blowing on something usually means we're kind of spitting on it, too."
"That means we're adding more germs into the mix," she says. "Pediatricians tell us not to 'clean' off our babies' pacifiers with our own mouths for this very reason."
"Yes, that technically means when someone blows out the birthday candles we're getting some germs there, too. Sorry to spoil the party!"
Dr. Jorge Parada, director of the infection prevention and control program at the Loyola University Health System, suggests we adopt a new rule of thumb.
"Instead of applying the five-second rule to a dropped food item," he says, "people should employ 'when in doubt, throw it out' as the golden rule."
"It may be annoying to have to wait in line for another ice cream cone for your child, or to butter another piece of toast -- but it beats the potential to become ill."