If you haven’t heard of the “five-second rule,” it’s the myth that it’s okay to eat a piece of food dropped on the floor if it’s picked up within five seconds. The rationale behind this is that fewer germs will stick to a piece of food if it’s picked up immediately. Plus, if nobody sees you do it, then what’s the harm? Plenty.

Bacteria doesn’t sit on the sidelines and wait five seconds before contaminating something. The damage is done instantaneously. Did you just drop a cookie, utensil, or other unprotected item from the breakroom? Throw it out, and don’t eat it yourself or put it back!

A story titled, “Is There Really a Five-Second Rule about Food on the Floor?” on CNN’s website says that urban myths like this shape our beliefs about when food is safe to eat. According to the story, more than two-thirds of women and more than half of men were aware of the five-second rule and that women were more likely to eat food that had been dropped.

I have a feeling that more than a few of us have eaten food off the floor (or other surface) and have been perfectly fine afterward. So, why is eating food off the floor so dangerous? It depends on many factors including a person’s age, health, and surprisingly, what surface the food was dropped onto. According to the CNN story, it didn’t really matter how long something sat on a surface. A 2007 study done at Clemson University found that the amount of bacteria was virtually the same whether the food was on the surface for five, 30, or 60 seconds and whether the bacteria was on the surface for two, four, eight, or 24 hours. What did matter, however, was whether the surface was carpet, tile, or wood and how much bacteria was on that surface in the first place. When a piece of food landed on carpeting, less than 1% of the bacteria was transferred, but when the food made contact with tile or wood, then between 48% to 70% of the bacteria transferred onto the food.

It’s important to note that while 1% might seem tiny, that’s still millions of bacteria and as little as 0.1% is enough to make someone sick. If the strain of bacteria is especially virulent, then as few as 10 cells can cause severe illness or even death in people with compromised immune systems. And the floor isn’t the only surface to be concerned about. Other surfaces, when unprotected, are just as bad and include utensils, plates, hands, etc.

The key message here is not to take a chance with your food or the food of your co-workers. Keep surfaces clean and remember the mantra of “when in doubt, throw it out.”