Have you been vaccinated against hepatitis A?  

It’s the time of year when candy, nuts, and other food becomes more prevalent on side-tables, in buffet-lines, and in office kitchens.  Before you reach into the communal bowl of your favorite holiday treat, you may want to consider where the hands of the person who came before you have been.  

Hepatitis A and other communicable diseases can be transmitted through a fecal-oral route, so if the person who indulged in some of the almonds from that bowl skipped washing their hands after a trip to the bathroom, you could get more than you bargained for in your next bite.  

The perils of communal food extend beyond foods that stand alone.  Undergraduate researchers at Clemson University recently published a study titled, “Effect of Biting Before Dipping (Double-Dipping) Chips on the Bacterial Population of the Dipping Solution.” (pdf) 

During the study, which was inspired by an episode of Seinfeld, researchers found that double-dipping does increase bacterial counts in dips.  

Three separate experiments were conducted to determine various factors that would affect bacterial transfer and the population of bacteria in dips.

What these researchers found was that three to six double-dips in one bowl transferred about 10,000 bacteria from the double-dippers’ mouths to the remaining dip.  In general, thicker sauces tested had lower bacterial counts than other dips.  Salsa was found to have the highest levels of contamination, possibly because it is runnier and bacteria can slip off the chip and back into the bowl easier.  

Eating dip that has been contaminated by double-dipping could make you ill if a double-dipper has pathogenic bacteria in their mouth.