The study was conducted by Prof. Paul L. Dawson, a food microbiologist, who decided to experiment with “double dipping” after watching a Seinfeld re-run in which a character named “Timmy” objects to George’s dubious dipping habits.
Professor Dawson told the New York Times that he expected “little or no microbial transfer” as a result of double dipping.
He was wrong.
Double dippers are just as gross as you’ve always suspected:
The team of nine students instructed volunteers to take a bite of a wheat cracker and dip the cracker for three seconds into about a tablespoon of a test dip. They then repeated the process with new crackers, for a total of either three or six double dips per dip sample. The team then analyzed the remaining dip and counted the number of aerobic bacteria in it. They didn’t determine whether any of the bacteria were harmful, and didn’t count anaerobic bacteria, which are harder to culture, or viruses.
There were six test dips: sterile water with three different degrees of acidity, a commercial salsa, a cheese dip and 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.
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.
Yuck. So, what now? “The way I would put it is, before you have some dip at a party, look around and ask yourself, would I be willing to kiss everyone here? Because you don’t know who might be double dipping, and those who do are sharing their saliva with you,” says Professor Dawson.