Double Dip Yuck

You invariably see it happen at get-togethers: double dipping. As microbiologists, we know that's risky business ' not to mention yucky business!

Let's start with a dip vehicle, the cracker. Scientists discovered once a cracker has been bitten, it carries a thousand times more bacteria than an unbitten one. To test what happens when you dip them, they used commercial chunky hot salsa, chocolate syrup, and cheddar cheese dip produced by well-known companies.

Before dipping, none of the dips contained detectable bacteria. After double dipping, they all had bacteria but the salsa had hundreds of times more than the other dips. And with every double dip, you're also enjoying thousands of your friend's bacteria. More bacteria gets spread into the salsa because it's less viscous, plus more of it drips back into the bowl from the half bitten cracker.

The oral microbiome is a complex mixture of about seven hundred different types of bacteria that live with each person. Only half are even named. Oral bacteria cause dental cavities and gum disease. They also include ones that can infect the heart, brain, intestines, and liver. People also have viruses, fungi, protozoa, and archaea in their mouths. Some viruses include HIV, hepatitis, mumps, rabies, herpes, and the flu.

Our mouths contain twenty billion bacteria and then add who knows how many of the other microbes and you have a virtual zoo that people are sharing by double dipping. Our advice is to limit your sharing at a party to nice conversation and keep your microbes to yourself.