I’m sure you’ve all been sensitized to the fact that you shouldn’t double dip your food, that is to say dip it into a communal serving bowl after it has already touched your mouth. I’ll admit to double dipping if I’m the only one using the dip (or if I’m using it with a select few, such as the Engineer, and I’ve got prior permission). If it’s a communal dip, however, after the first bite, I turn the chip around and dip a piece of it that hasn’t come into contact with my mouth.
Some of you will of course remember the Seinfeld scene where George Costanza gets chastised at a party for his lack of double dipping etiquette! The memorable line is “That’s like putting your whole mouth in the dip!” So the Mythbusters, bless their souls, decided to put this to the test. They counted how many bacteria would be found in the dip prior to any dipping, after one “tainted” dip and... after someone swishing dip in their mouth before spitting it out into the bowl. It turns out that, while some extra bacteria might appear after a double dip, it is nothing to be concerned about, and nothing as bad as the bacteria appearing after one’s whole mouth as been in the dip!
Here’s a link to the article on The Kitchn, where you can see both the Seinfeld clip and the Mythbusters one (which does have explosions, though not of the dipping variety).