They say do one thing every day that scares you, but ideally that thing shouldn’t involve putting questionably contaminated bits of food in your mouth. Growing up, many of us adopted the behavioral trait of yelling “Five Second Rule!” as we snatched up an escapee sausage from the floor, but is there any truth to there being a time limit on pathogen accumulation?
As kids, we’re taught that germs are everywhere and with time (or in the face of a deadly global pandemic) we pick up the names of some of the usual suspects. Early estimates put the shelf-life of SARS-CoV-2 on surfaces at around three days. That's a big window for sausage dropping and retrieval.
Surface germs are a big problem in places like gyms where lots of people are volunteering their bare skin to sweaty benches and mats: environments where Staphylococcus bacteria thrive. This particular group of germs like to get all up in your skin causing oozing lesions that are highly contagious.
Five Second Rule: How does time influence contamination?
So, how would a sausage fare rolling across your kitchen floor? Does time affect the ability for objects to pick up pathogens? Is a sausage retrieved in five-seconds-flat any safer to eat than one that’s lingered for a skin-crawling five minutes?
“There has actually been some research into how much bacteria can be transferred to food within five seconds,” said infectious diseases specialist at Addenbrooke's Hospital, UK, Dr Dominic Sparkes to IFLScience. “It depends a bit on the surface, however.
"On tiled surfaces as much as 99 percent of bacteria were transferred onto the piece of food (in this study, a piece of bologna). So, your five seconds is probably ample time to transfer potentially pathogenic bacteria onto your food, in fact any period of time on the floor is probably too long.”
Bad news, then, for the bereft sausage dropper. But isn’t a little bit of a bacteria okay every now and then?
“While it’s true most bacteria are unlikely to cause any gastrointestinal illness, there are some – salmonella, for example – which not only cause gastroenteritis but can also survive for long periods of time on surfaces. Even small quantities of these bacteria can make you unwell.
“There are other bacteria which are often found in the environment which produce toxins. For example, Bacillus cereus. When ingested these toxins induce vomiting and your food is much more likely to pick up these organisms if it rolls across your kitchen floor. Work surfaces generally are cleaned thoroughly, killing these bacteria. Most domestic kitchen floors however are rarely cleaned so extensively, and so the risk of your food picking up pathogenic organisms is much higher on the floor than your kitchen top.”
*Gingerly puts fallen sausage in the bin*
Five Second Rule: Where did it come from?
Like many colloquialisms, the exact origin of the Five Second Rule is unclear. According to a report from the Huffington Post, the food safety approach has ties as far back as Genghis Khan – the first Great Khan of the Mongol Empire whose reign began in 1206.
Supposedly, the notorious leader had an “if it’s good enough for me, it’s good enough for you” rule about eating fallen food. Not so oppressive at the five-second mark but a little authoritarian if it’s a four-hour matured pool of floor yogurt.
Whether the Five Second Rule trickled down from the grubby kitchen floors of the Mongol Empire to modern-day isn’t clear and it’s unlikely we’ll ever know for sure. One thing that seems to be certain, however, is that there’s no scientific backing for the safety status of your food suddenly switching from seconds five to six. Not that it necessarily stops many of us, mind.
“Of course, that goes totally against my actual practice which is to eat whatever I find on the floor regardless of the length of time it has been there," concluded Sparkes.