Everyone knows that double dipping is gross, but there's always that one friend who can't seem to finish the chip in their hand before sending it back down to the guacamole. But scientists have shown that not only is this bad manners, it also really does spread a whole lot of germs.
As the Tech Insider video above explains, at the end of last year, researchers from Clemson University dunked whole and half-eaten chips into a glass of water to figure out how much bacteria each of them could pass on.
The water dipped with the bitten chip contained 1,000 more bacteria per mL of water than the one exposed to the whole chip. But water is one thing, what happens to real sauces?
The team tested out salsa, cheese dip, and chocolate syrup to see if the same thing occurred with thicker liquids. They found that right after a double dip, all the sauces contained more bacteria than they did when they were dipped with an unbitten chip.
But the salsa got the worst deal - immediately after double dipping, it had more than five times more bacteria compared to the other two sauces.
The researchers think this is because salsa is watery, so contaminated bits are likely falling back into the bowl after dipping.
"The lower viscosity means that more of the dip touching the bitten cracker falls back into the dipping bowl rather than sticking to the cracker," Paul Dawson, leader of the Clemson University study, wrote for The Conversation last year. "And as it drops back into the communal container, it brings with it bacteria from the mouth of the double-dipper."
The good news for salsa lovers out there is that, because salsa is so acidic, it actually kills bacteria quicker, so within 2 hours, the bacteria levels returned to the same levels as the other two sauces. Although we're not sure how often salsa lasts 2 hours at a party...
So how bad is it to get bacteria from someone else's mouth into your own? Well it all depends on in if they're sick or not.
We all have hundreds to thousands of different bacteria types in our saliva anyway - scientists just found a new life form in there last week! - so it isn't necessarily a terrible thing.
But, as the video above explains, there are a whole lot of nasty illnesses that can be spread through our mouths, so it all depends on how much you trust the person you catch double dipping.
Check out the video above to assess your risk, and please, for the love of salsa, don't double dip in public. Science says no.