All of us tend to eat the food which has fallen on the floor. We have already taken that food and swallowed it.
We are invoking the 5-second rule, but is it OK to eat foods that have been dropped on the ground?

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According to Don Schaffner, extension specialist and professor at Rutgers University says, “I like to tell people about the science and let them make the decision. When a portion of food is dropped on the ground, it may contain germs that can make you sick.”
Where Did The Five-Second Rule Originate?
No one knows where the five-second rule originated, but it is attributed to 13th-century Mongolian ruler Genghis Khan, who has had a rule that the food that fell on the ground would remain there as long as it was deemed suitable.
According to the book “Did You Just Eat That?” written by Dawson and Brian Sheldon. People of that era were unaware of micro-organisms and how they cause the disease, so eating food on the floor may not have been a big deal.
Is The Five-Second Rule True?
Paul Dawson, professor at Clemson University, said, “It is pretty much a myth.” “It depends on what is on the ground and where the food lands.”

timesofindia.indiatimes.com
He explained food will detect bacteria right away, “so you are just gambling if you eat it and you are not sure what is on that surface.”
Foodborne illness, caused by salmonella and other bacteria, can cause nausea, vomiting, or diarrhea and even be fatal.