Don't worry—the cookies are safe.
Everyone remembers the iconic Seinfeld episode that alerted us the now-feared practice of double dipping (“That’s like putting your whole mouth right in the dip!”). But even if you were on George’s side, you probably know that most people were not—seeing it as a sign of bad manners and poor hygiene. Unfortunately for hungry party-goers, a new health study from Clemson University isn’t on George’s side either. In fact, researchers found that going for a little extra salsa on your half-eaten chip spreads much more bacteria than you think.
Inspired by the Seinfeld episode (or so they say in Scientific American), researchers from the university, lead by Dr. Paul Dawson, investigated how gross double-dips really are. Their findings were published in the Journal of Food Safety. To do this, they conducted three experiments: two with water, and one with actual food. They began by testing how much bacteria transferred to water from whole and half eaten crackers. Water contaminated with pre-bitten crackers had 1,000 more bacteria per millimeter. Yuck.
Then, they adjusted the pH of the water to better match the acidity levels of popular snack dips, since acid typically kills bacteria. Unsurprisingly, they found that the more acidic liquids actually had decreased levels of bacteria over a period of two hours.
Once they moved onto real food, the results become a little bit, well, disgusting. They tested three all-time favorite dips: a salsa, a cheesy dip, and a chocolate dip. If these are your favorite party foods, now would be the time to stop reading. They tested bacterial spread from bitten and unbitten crackers, and monitored the dips over a period of two hours to see how bacterial colonies grew. If you’re a chips-and-salsa devotee, bad news: Salsa took on five times more bacteria compared to chocolate and cheese dips, likely due to the differences in thickness. Scientists theorize that because salsa is more fluid, it’s more likely to drip back into the bowl as you’re lifting the germ-infested, double-dipped chip into your mouth. Cheese and chocolate are safer (sort of), because their thickness means both stick more easily to the cracker.
However, salsa also happens to be more acidic than the other two options, meaning that after two hours, scientists found its bacterial levels had decreased to match the cheese and chocolate dips.
Given this new information, you have two options: Either avoid the chip table altogether at your next party, or BYOD (bring your own dip).