“Yes and no,” Brain, who holds a doctorate in hygiene, writes in an e-mail.
“Yes, the longer it’s there the more likely someone or something will step on it and further contaminate it. Also as time increases, perhaps the certainty that you know that you dropped it and it’s your food decreases. Eating floor food of unknown origin sounds at least unpleasant and probably unhealthy to me. [But n]o, I think food picks up as many germs/debris in 0.1 sec as it does in 5 sec or 50 sec or 500 sec.”
“Unless you are in a place where serious pathogens are likely, eating dropped food sounds okay to me—although it may not impress your date. But then dropping food on the floor has already cost you points anyway. Question: Which has more human pathogens, the floor or your spouse’s/partner’s/date’s mouth? It’s definitely not the floor, but I quite enjoy kissing. Finally, wait until you have kids and you hug and kiss them—even or especially when they are sick. That leads to interesting exposures. We don’t live in a germ free world, but fortunately we have great host defenses and a vigorous immune system.”