Explanation: This myth gathered steam after a Seinfeld episode aired in which George was caught in the socially unacceptable act of double-dipping. The theory here is that double-dipping — placing a chip in dip, biting off the chip and then placing it again into the dip — spreads as much bacteria in the dip as if you'd stuck your whole mouth in the bowl. So, MythBusters Adam Savage and Jamie Hyneman set out on a bacteria-finding mission with somewhat surprising results.
By testing bacterial growth in petri dishes using sterilized chips and a salsa-like substance, they found that double-dipping adds just a small amount of bacteria to the salsa, and definitely not as much as sticking your mouth in the bowl.
The truth is that most dips — store-bought or homemade — already contain bacteria. Double-dipping adds only a few more microbes than the multitude swimming in your salsa to begin with.
So, if you want your dip to stay totally bacteria-free, it looks like you're out of luck. But if you want to keep your germs to yourself, your best bet is to just eat out of your own private bowl.