“Double dipping” your chip: Dangerous or just…icky?

Robert H. Shmerling, MD

Senior Faculty Editor, Harvard Health Publishing

Double dippers are everywhere – the 4th of July barbeque, family reunions, Super Bowl parties, anywhere chips and dip are a staple. These are the people who take a bite and dip their chips a second time when they think no one is looking.

Just ask George

Leave it to George Costanza on Seinfeld to make double dipping a mainstream public health scare. The episode, which originally aired in 1993, brought shame to George as he was caught dipping a chip a second time at a wake. The partygoer objecting to this practice exclaims “That’s like putting your whole mouth right in the dip!”

But is double dipping really so bad?

Ever since that Seinfeld episode, the “health menace” of double dipping has been a mainstay of party conversation, high school science projects, and even high-level academic investigation. Perhaps the most influential was a 2009 study performed at Clemson University and published in the Journal of Food Safety, entitled “Effect of biting before dipping (double-dipping) chips on the bacterial population of the dipping solution.” The title alone may be enough to make you lose your appetite.

The researchers carefully analyzed bacterial contamination before and after a person double dips. Here’s what they found:

  • Bacterial counts in the dip increased significantly after a person took a bite from a chip and then dipped again.
  • The number of bacteria contaminating the dip varied depending on the dip – salsa had more bacteria after double-dipping compared with chocolate or cheese dips (perhaps due to differences in thickness and acidity of the dips).

Similar findings were noted when bacteria counts were measured after a bitten chip was dipped in water.

So just how risky is double dipping?

It’s important to note that this research was not designed to find people who became sick because someone else double dipped. And, considering that our mouths are normally packed with bacteria, it doesn’t necessarily follow that more bacteria in the dip means double dipping is dangerous.

However, this research does raise the possibility that a person who is sick (or about to be) might spread a disease by re-dipping a chip. Documented examples of this are hard to find – if you know of one, let me know! But even if the risk is hard to prove, the risk may be real. We know of many respiratory diseases that can be spread by contact with saliva, such as influenza (the flu) or whooping cough. Still, there are probably much bigger risks at your next office party than double dipping. You’re more likely to contract an illness from a sick person coughing or sneezing in your face or if they don’t wash their hands while sick than you are from a healthy double-dipper. So, while it’s reasonable to discourage double dipping, it’s unlikely to pose a major risk to your health.

And if you’re a double dipper…

And, for habitual double-dippers, I wonder about a more responsible option: turn the chip around to double dip from the unbitten end of the chip. Stand by – somewhere in America there is a high school kid setting up that experiment right now.


  1. Tony

    I’ve never seen this double-dipping. The usual practice is to scoop some of the dip on to our own snack plates, and use that for whatever chips we take.

  2. choosefan

    i think Bacteria come 1st Food Poisoning, and Bacteria are everywhere: in water, air, and the bodies of every human and animal.

  3. Chong

    Hey! I know this is kinda off topic nevertheless I’d figured
    I’d ask. Would you be interested in exchanging links or maybe guest writing a blog post or vice-versa?
    My website goes over a lot of the same topics as yours and I feel we could greatly benefit from
    each other. If you might be interested feel free to shoot me an email.
    I look forward to hearing from you! Superb blog by the way!
    authentic jerseys china free shipping

  4. Robert Edelberg

    The comment is made that there is more risk of having someone cough or sneeze in your face than in double-dipping. But someone need not cough or sneeze to create a risk. If you have ever watched a person speak into a sunbeam that is streaming through a window, you may be amazed at the spray of finely divided saliva that one discharges from the mouth when speaking.

  5. Wendy

    Can I safely break a large chip into three parts and serial dip?

  6. Gretchen

    Just another lame article using up time and space. You have to realise universities must struggle to put out something to engage the “layperson” and keep their name in your mind in case you contract a severe (expensive) illness. Sometimes they really do produce something that is an answer to a nagging problem that will benefit us all, but this was a total miss. Talk about watering down data (or actually, what data?). Harvard? Come on. Don’t you think your readers deserve a bit more respect?

  7. Janis M

    I concur with Yasmin’s comment. There are forms of information, they don’t all have to be in rigorous science format. There is no need for ego competition. Reference to popular culture, such as, Seinfeld is a good vehicle for putting a message out to a wider audience than the already converted. I have witnessed double-dipping being practised locally and internationally and aside from health concerns, I find it discourteous and it demonstrates a lack of consideration for others.

  8. liz b

    I have just started a course if chemo so thank you as i would dip a chip without thinking someone else has been double dipping so i can now avoid!

  9. Phillip Hughes

    I enjoyed the article. Note to self, “Do not read the comment section on Harvard Health. While not objectively researched, qualitative data suggests reading the comments section may cause frustration, anxiety or true upset.” While I understand the importance of excellent research, I gather from the use of a Seinfeld episode being cited throughout, that this article may have been created more for light-hearted entertainment in contrast to sharing rigorous proof.

    • Christina

      Likewise, skipping over some readers’ negative, grumpy, mean spirited and/or foul comments upon political news articles may also be beneficial to one’s health. 😊

  10. Ron Morton

    Who eats chips with dip today ?

    The only people that I know are on Seinfeld reruns.

  11. Yasmin wallani

    This article helps you practice SAFE HYGIENE, be Thankful and follow, why always trying to counter, and stop good ideas coming your way, or if you cant stand taking good advice just keep quiet, THANKS

  12. Ken Running

    Absolutely a 3rd grade blog. Consider kissing, taking a sip of friends wine. If Harvard and AARP are that squeamish, then drop me from your list.
    I plan to notify Harvard Med booklets and lady chief of AARP. No place in world for wussies giving ill advised advice with no facts to back it up. God help your children and spouses.

  13. Ron T

    The operative thing here is the possibility of increased risk where the dipper has an illness that can be transmitted by saliva. When a transmittable pathogen is not present there is not a risk from otherwise healthy saliva that contains innocuous bacteria, in fact, there is increasing evidence that a greater diversity of gut flora is beneficial to general health.

  14. Meddy

    “But even if the risk is hard to prove, the risk may be real. We know of many respiratory diseases that can be spread by contact with saliva, such as influenza (the flu) or whooping cough.” Were either of those risks hard to prove? What do you mean by “hard to prove?” What examples do you have of risks that could not be proven, but were nonetheless real?

  15. Maty

    If you think double dipping is not good what about being at church and drinking the wine from the same cup as maybe 30 other people ,I know they wipe the cup after each use but use the same napkin is used is this really healthy .

  16. Mary Baine Campbell

    This is totally wack! All human beings since Adam and Eve “double-dip”! In my 62 years on the planet, attending barbecues and parties and receptions, I have never met anyone who felt the slightest shame about it. Next thing I know you’ll try to make us feel anxious about kissing–even worse, from this weird POV! I like barbecues, guacamole, salsa, my fellow humans, and kissing. Lighten up.

    • Helen B

      I don’t think I have ever seen anyone double dip. Most people spoon some dip onto their own plate and put their chips there.

    • Lee Esquibel

      Although having attended many gatherings, in my 82 years, at which chips and dips were served, I can’t say how many were shamed about blatant double dipping because I didn’t take a poll. However, since I recently started paying attention, I have not seen double dipping taking place. I imagine that the ickyness of the practice is now well known enough that most gatherings are not afflicted by unsanitary practitioners. As to kissing, unless one is a serial kisser at gatherings, where one may not know many of the attendees personally, I don’t think there would be a problem.

  17. Debra California

    I am not sure suggesting the alternative of dipping the other end is better with the bacteria on the fingers that held it to dip the first time sure to contaminate the dip.

  18. Sean

    I have a few questions about the validity of this study, is there an outline of their methodology? Did the researchers check to see if dips gained bacteria from a regular chip dipping (no double dipping). I could see that maybe the chips themselves harbored some bacteria to begin with, or the action of someone touching a chip and dipping it could transfer bacteria.

Commenting has been closed for this post.