Is there any actual danger involved in double dipping (dipping your food into the common dip or sauce after you’ve already taken a bite out of it)? What (if any) maladies can be spread this way, and under what circumstances, and what are the true odds of catching them?
Note that I’m posting this in GQ in hopes of getting a factual answer from someone who actually knows something. Opinions and speculations can go in the MPSIMS thread.
As a Microbiologist I’ll say that yes, it contaminates the dip guaranteed (as the previous poster’s study shows), but there’s a lot of other factors that determine whether or not you’ll get sick. For starters, the “contaminants” are probably just standard mouth bacteria (I believe there are >400 species) which probably grow in your mouth anyhow, and secondly, an infectious dose in most cases is higher than what you’ll get from a double-dipped dip. Generally you need hundreds of thousands or millions of bacteria to get sick, and the amount on a double-dipped chip is probably tens of thousands (an educated WAG), and they probably don’t divide too well at the room temperatures found in dips. On top of that, dips contain salt and other preservatives that probably kill bacteria.
It reminds me of the wine cup at church - I’m not sure why so many people drink from the same chalice, but I really don’t see massive plagues resulting from it so on the whole I’m sure it’s ok. Of course, as a Microbiologist I still refuse to drink from that cup, or use a dip that’s been double-dipped into, but once you know what I know you become hyper-OCD!
In the Church of England, the communion wine is a fortified wine (a port or similar) with a token amount of water added. This means the alcohol percentage is about 20% or there about - whether this is enough to kill bacteria and viruses, I’m not sure. There is almost certainly a risk, but I’ve never, ever seen anyone get something that they can point to as caused by the chalice, and I’ve been an Anglican for a long time. Personally, if I have a cold or similar, I “intinct” (dip my wafer in the wine) - not a particularly CoE behaviour, but polite in the circumstances. I do have a problem with shared chalices containing non-alcoholic grape juice.
As I noted in the other thread, when we run a Chocolate Fountain, we stop people from double-dipping. The melted chocolate is warm and full of sugar, and running for several hours. In that time, a small amount of contamination could easily grow into a serious public liability issue. We would also shut down if a guest stuck their tongue, face, hand etc in the fountain.
The funny thing about chocolate fountains is that the chocolate is at body temperature and has a similar heat capacity. When you get it on you, you often don’t notice. Sometimes we get people who drop a dip in the bowl, and try to spear it again. Concentrating on the item, they will get chocolate all over their hand without even noticing - we try to prevent that.
I believe the Master himself said that trying to kill bacteria with alcoholic beverages is not going to get you anywhere, since the dose of alcohol you would need to put a dent in the Bad Bacteria would also kill enough of the Good Bacteria to put your life in danger. That said, it can’t be much less effective at killing germs than communal ecclesiastic savior-vampirism is at spreading them, I suppose; and it’s a good excuse to have sake with your sushi, which is what matters at the end of the day.