No harm done.
Or is there? Contrary to common belief, new studies show that even if you pick up a dropped item within seconds it is still crawling with bugs.
Researchers at a leading American infection prevention and control programme say the so-called “five second rule” actually does little to guard against bacteria.
Instead, says Jorge Parada, medical director of the Loyola University unit in Illinois that carried out the research: “A dropped item is immediately contaminated and can’t really be sanitised.
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“When it comes to folklore, the ‘five-second rule’ should be replaced with ‘when in doubt, throw it out’.”
The truth is that all items that come in contact with a surface – whether floor, table or street – pick up bacteria.
Worse, when it comes to mummies and dummies, sucking the pacifier to ‘clean’ it before returning it to baby only doubles the bugs.
"That is double-dipping - you are exposing yourself to bacteria and you are adding your own bacteria to that which contaminated the dropped item,” says Parada. “No-one is spared anything with this move.”
He adds: “Sometimes it doesn't take a lot of bad bugs for you to get sick…Maybe the dropped item only picks up 1,000 bacteria, but typically the innoculum, or amount of bacteria that is needed for most people to actually get infected, is 10,000 bacteria - well, then the odds are that no harm will occur.
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“But what if you have a more sensitive system, or you pick up a bacteria with a lower infectious dose? Then, you are rolling the dice with your health or that of your loved one."
However he does concede that dropping a crisp on a clean table will result in fewer bugs than dropping a slice of cheese on a dirty pavement.
Yet the ‘five second rule’, he adds, is little more than a “polite social fiction we employ to allow us to eat lightly contaminated foods”.
Surely, though, a few bugs and bacteria can only be good for the immune system?
"There actually is certain research that supports the importance of being exposed to bacteria at critical times in a child's development," said Parada. "But I believe this development applies to exposures of everyday living.
“I do not advocate deliberately exposing ourselves to known contaminants. That would probably be a misplaced approach to building up our defences. If you want to be proactive in building up your defences, eat right, exercise, and adequate sleep - and remember to get your vaccines."