It’s the second most noxious party faux pas, after getting drunk and hitting on your boss’s wife: double-dipping. Made famous by the Seinfeld sketch in which George Costanza is yelled at by his girlfriend’s brother while at a funeral reception (the brother, aghast, accuses George: “You dipped a chip, you took a bite—and you dipped again!”), double-dipping is one of those habits that some people deplore and others shrug off.

Now, just in time for Super Bowl Sunday, a study has been released offering scientific evidence that those who deplore double-dipping have been right all along. In the study, a Clemson University food microbiologist (incidentally, the same guy who disproved the five-second rule) had nine students take a bite of a wheat cracker and then dunk it in a dip for three seconds. “There were six test dips: sterile water with three different degrees of acidity, a commercial salsa, a cheese dip and chocolate syrup,” the New York Times reports (chocolate syrup?!). “On average, the students found that three to six double dips transferred about 10,000 bacteria from the eater’s mouth to the remaining dip.” The article continues:

Each cracker picked up between one and two grams of dip. That means that sporadic double dipping in a cup of dip would transfer at least 50 to 100 bacteria from one mouth to another with every bite.

The kind of dip made a difference in a couple of ways. The more acidic water samples had somewhat fewer bacteria, and the numbers of bacteria declined with time. But the acidic salsa picked up higher initial numbers of bacteria than the cheese or chocolate, because it was runny. The thicker the dip, the more stuck to the chip, and so the fewer bacteria were left behind in the bowl.

Ten thousand bacteria! The rules for Super Bowl are clear: tiny chips, thick dip, and NO DOUBLE-DIPPING.

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