Using the three-second rule when dropping food or a child's dummy on the floor could pose a risk, new research shows.
Five food items and a child's dummy were tested by Manchester Metropolitan University (MMU) to see whether the three-second rule could be trusted.
The scientists, who carried out the survey on behalf of cleaning experts Vileda, discovered E. coli on the dummy after it had been dropped on the floor.
MMU Technical officer Kathy Lees said: "The child's dummy, which all our case studies admitted dropping on the floor regularly and then returning to their children, showed very low levels of E coli.
"We also discovered Pseudomonas - bacteria which could potentially lead to respiratory, tissue and urinary tract infections, for those whose health is already compromised."
The scientists also tested the theory by dropping bread with jam, cooked pasta, ham, a biscuit and dried fruit on the floor and left them there for three, five and 10 second intervals.
They found foods with a high salt or sugar content are safer to eat after being retrieved, with less chance of harmful bacteria surviving on such items.
But the dried fruit and cooked pasta showed signs of bacteria in three seconds.