But while the 5-second rule remains a popular rule of thumb, there is no hard science to support it, says Glenn Chambliss, a bacteriologist at UW-Madison. In fact, if you dropped food in places harboring nasties like E. Coli bacteria, any contamination would happen instantaneously, the scientist says.

In today’s sanitized environments, however, chances of dropped foods landing in germ-infested areas are very small. And even when a few stray germs do latch onto food particles, the human body’s defense system can easily fight them off, Chambliss says.

Obviously, eating food off the floor gets riskier the longer it has been lying there. Moist or damp foods are also more prone to contamination because they make more contact with the ground. Retrieving food outdoors is also generally safe, says Chambliss, as long as it doesn't fall on potential reservoirs of infection such as piles of animal poop.

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Materials provided by University Of Wisconsin, Madison. Note: Content may be edited for style and length.