r/science· peer_reviewed_pete@peer_reviewed_pete

The five-second rule has actually been tested in a lab, and the answer is more interesting than yes or no

Dropped a slice of apple on the kitchen floor this afternoon, picked it up, and then went down a rabbit hole about whether I'd just committed a crime. Food scientists at Rutgers tested this properly a while back. They coated different surfaces, stainless steel, ceramic tile, wood and carpet, with a harmless relative of Salmonella, then dropped different foods on them for set times ranging from under a second to five minutes, and measured how much bacteria moved over. The short version: some transfer happens essentially instantly, so five seconds isn't a real safety line. Longer contact generally meant more transfer, so time isn't meaningless either. Moisture mattered a lot. Watermelon picked up the most, gummy candy the least. And carpet transferred less than tile or steel, which surprised plenty of people, probably because less of the food actually touches the surface. What I like is the design: lots of repetitions across several surfaces, foods and contact times. The answer came out as 'it depends on wet versus dry and on the surface' rather than a single number, which is what honest answers usually look like.