In what is being hailed as the first study inspired by hit US comedy Seinfeld, researchers have proved you really shouldn’t dip your chip if you’ve already sampled it.

The controversial habit of biting off half a chip – or crisp as we say in the UK – and then re-dunking the remaining half actually does transfer bacteria from the mouth of the ‘double-dipper’ to the dip itself.

“The way I would put it is, before you have some dip at a party, look around and ask yourself, would I be willing to kiss everyone here? Because you don’t know who might be double dipping, and those who do are sharing their saliva with you” Paul Dawson, microbiologist at Clemson University, told the NY Times, which broke the story. It seems to me the reasons you don’t run round kissing everyone at parties aren’t solely to do with bacteria, but I’ll let that pass.

A team of Clemson undergraduates undertook to test whether double dipping transferred bacteria found that sterile water acting as dip contained “a significant amount” of bacteria as a result of this practice. A PDF of this reseach is available on Dawson’s website, it says

Whether the amount of contamination is dangerous to the dippers’ health or not is still debatable and can depend on multiple external factors including the type of chip/dip or the relative health/illness of the person whose mouth provided the bacteria. Next time you take a bite of your chip, however, and are tempted to commit a second dip, keep in mind that the numbers have been calculated, and the bacteria are having just as much of a party as you are.

The results will be published in a forthcoming issue of the Journal of Food Safety.