Double dipping (dipping a bitten chip in the salsa) transfers thousands of bacteria from your mouth.
Professor Paul L. Dawson, a food microbiologist at Clemson University, published the results of his students' study into double dipping in the Journal of Food Safety.
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.
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.
Professor Dawson likened the bacteria transfer to kissing everyone else at the party.