WE’VE ALL BEEN THERE – in that agonising moment where we’ve just spent a few minutes making a top-notch sandwich, or bought a snack from a shop… only to drop it on the ground pretty much immediately.

Until now we’ve had the comfort of the so-called ‘five second rule’ – a guide based on the premise that if you can pick up the food quickly enough, it won’t have picked up anything nasty from the floor and the food will still be edible.

Well, science – damn you, science! – has some bad news for you: it’s time to put the food down.

Researchers at San Diego State University have found that five seconds isn’t nearly enough time to save your food from infection by whatever germs are on the surface it falls on – though it depends on the sort of food you drop.

The Global Post points out that dried fruit can pick up dangerous bacteria in under five seconds. Pasta, meanwhile, can pick it up in just three seconds.

The scientists disproved the so-called rule by dropping carrots and baby bottles on different surfaces, including counter tops, tiled floors, carpets and the trays of high chairs.

They found that the carrots picked up more germs from a counter top than any other surface, followed by the tiling and then the carpeted floor.

Perhaps worryingly for many parents, though, dropping a baby’s bottle or cup on a high chair tray turned out to be the most dangerous surface to allow food to fall on – while the counter-top, which was the worst surface for a carrot, was the safest for the bottle teat.

Anyway, the moral of the story is: the next time you drop a sandwich? Bin it.

Image: Flickr/Christian Cable, via Creative Commons.