Dr. Gifford Jones

Dr. Gifford Jones

How safe is double dipping?

How many times will you see this happen during the holiday season? I’d predict several times unless you’ve decided to say “no” to parties. My bet is that someone will walk up to the table, pick up a shrimp, dip it into the sauce, enjoy the taste, and then dip again. And when I see this I wonder, “How safe is it to share the sauce in the communal bowl with them?” And, “Why didn’t their mother tell them not to do it?”

Since research on double dipping won’t win anyone the Noble Prize, there’s not much science on this topic. But the question did catch the attention of Paul L. Dawson, Professor of Food Chemistry at Clemson University, South Carolina.

What got Dawson interested was a re-run of a 1993 Seinfeld episode where George Costanza is attending a funeral reception. He double dips and is immediately confronted by his girlfriend’s brother, who says, “Do you know what you did?”

The result? Professor Dawson’s students decided to conduct some dipping experiments. They used wheat crackers and found that three to six dips in a bowl transferred 10,000 bacteria from eater’s mouths to the remaining dip. This means that if you’re at a party and three to six people double dip their chips, any chip you dip may pick up at least 50 to 100 bacteria.

But will this unhygienic practice make you ill? If you’re having a lucky day, you’ll most likely just live with someone else’s germs. But what happens depends on the number of bacteria you pick up, how many people double dip and most important of all, the type of bacteria present.

At this point you may be thinking, “I’ve double dipped for years and survived”.

If so, I wish you continued luck. But you can decrease the risk by being careful about what you dip into at a party.

For instance, Dawson’s experiments showed that thick dips such as cheese, chocolate and hummus are safer with fewer bacteria, and their number decreases over time. But you may get more than you bargained for by dipping into salsa which is runny allowing more bacteria to slip off the chip into the bowl.

Before double dipping also consider that saliva contains germs that can cause meningococcal meningitis. It’s potentially life-threatening infection that infects the covering of the brain and spinal cord. Picking up this infection is not a good way to start the holiday season.

What you dip into may also contain a variety of viruses such as the influenza virus and the cytomegalovirus (CMV). The CMV is normally in the respiratory system, but can get into saliva and affect a number of organs. It is especially dangerous for those whose immune system has been weakened by HIV, and those who have received an organ or bone marrow transplant. And there’s always the risk of mumps when double dipping.

What’s the risk of picking up herpes? It’s certainly possible, but how big a risk is hard to say. After all, for years researchers said that it was impossible to contact herpes by sitting on a toilet seat. They assured people that the virus quickly died when exposed to the air. But they were wrong.

Dr. Trudy Larsen, a researcher at the University of California, another one who won’t win the Noble Prize, asked a patient with an open herpes sore to sit on a toilet seat. She then took cultures several hours later and found that the virus was alive and well. Sitting on a public toilet seat has never been a good idea.

What do I do when I see a bowl of shrimps at a party? I like shrimps so I always take one or two if I’m the first to arrive. But if the crowd has gathered around the communal bowl I’ll get my shrimps or whatever else can be dipped into elsewhere. I’ve never enjoyed sharing other people’s germs, even those of good friends.

Double dipping is like saying to yourself, “Do I want to kiss everyone at this party?”

I’m sure my mother would have told me that’s not the proper way to behave. And I’m sure she would say the same about double dipping.

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