When you blow out birthday candles are you putting bacteria on the cake?

Answer 1

I can't imagine that a person wouldn't be transferring bacteria among other things onto a cake when blowing out the candles. However, I'm not sure this is really an issue of concern (unless the person blowing is sick), as there are bacteria and other undesirables floating in the air and all around us all the time anyway.

From Davidh305:

That answer may reflect more a lack of imagination ("I can't imagine") than an abundance of facts. Bacteria in the air don't multiply easily; those in throats and mouths, however, have much more media to grow on.

Not all germophobia is irrational. There are strains of germs these days that are resistant to medicine, and that virtually nobody has developed immunity to. Candles do not magically neutralize germs; and neither does white icing. If you would object to a waiter blowing on your dinner, or a donut maker blowing on your donut, what difference is there between that and blown-on birthday cake?

There are now numerous studies (including Clemson Univ.) that show that blowing out candles on a birthday cake is indeed a vector for spreading both bacteria and viruses to others. While this is not very significant within a family -- who have probably already shared all or most of one another's germs -- it is significant when a houseful of visiting kids (or adults) eat cake that has had not just germs, but also saliva (ick) sprayed upon it.

There are several different issues:

1/ It's worse when kids do it.

Kids have "new" immune systems, so they're experiencing (and carrying) a variety of germs for the first time. Most adults have antibodies that will quickly suppress a variety of cold, flu and other viruses they've already encountered; but kids haven't developed those antibodies yet. So a kid's more likely to have new and active strains to spread, and in large quantities. Kids bring home most of their germs from school, and from birthday parties.

2/ While breath alone can carry germs, the presence of saliva droplets (which germs can cling to) will much increase the contamination.

Kids in particular, with small lung capacity, don't have much "power to their puff" -- so they are more likely to blow around their tongues (to accelerate the wind flow), and thus to spray saliva on the cake, than adults. (Even worse: when five other kids also blow on the candles to "help" the birthday child!) But even adults can't help but spit: Try blowing on a mirror up close, with the same power and length as you would use to blow out birthday candles. Now look at the mirror up close. Ick.

3/ You can't tell who's sick.

It is during the incubation period -- usually the first 2-3 days, for a cold or flu virus -- that the virus is multiplying out of control in the body. But there are no symptoms yet!! The symptoms come later, and are due to the body ramping up its immune response. The person who's sneezing and coughing is already fighting the disease -- and is, paradoxically, likely less contagious than he was when there were no symptoms.

Moreover, nobody gets sick immediately, because they have their own incubation period. So if half the guests come down with something days later, the cake, candles and spit are not likely to occur to them as a cause.

4/ Some of the recipients who share the cake may be more susceptible.

Many people have imperfect immune systems -- especially the young, the elderly, cancer or HIV patients, people recovering from surgery, etc. While most people might shrug off a few germs, these folks could have life-threatening consequences. People with ulcers or GERD on medicine to suppress stomach acids, like Pepcid, Zantac, Tagamet etc., might have greater susceptibility to food-borne pathogens, because stomach acid would normally kill most of them. Drug addicts and alcoholics also usually have suppressed immune response, even after getting clean for a while; and meanwhile, lots of NA and AA groups celebrate a year clean or sober with a cake and candles!

5/ Sugar.

Most kids' birthday parties feature more sugary foods and drinks than just the cake. While germs do not grow in sugar, sugar does affect the system as a whole. Many people, subjected to a sudden huge sugar influx, will experience first a rush, then a crash. It is during the crash that the vigor of immune resistance may be reduced.

6/ Attachment to rituals.

The reason to blow out the candles? Because they're easier to remove from the cake when no longer lit! People associate the blowing with making a wish, and voila -- a ritual enforced with the power of belief. While adults enjoy the ritual, kids are positively addicted to it, and may even think that the more flamboyant the "spray and display", the better! Many kids feel cheated if their birthday cake lacks candles, and the obligatory ritual. (Many adults, too.)

There are several remedies:

a/ Gently cover the cake with wax paper before inserting the candles; when removing the blown-out candles, peel off the wax paper too, and throw away the germs.

b/ There are now patented "cake shields" (usually made of clear plastic) that candles can be inserted into.

c/ There are now patented (disposable) blowing devices: you still blow through them, but they have a filter to contain germs and saliva.

d/ Best of all: A separate small cake with all the candles on it, just for the birthday girl or boy; and a bigger one (kept aside and covered till the spitting is over) for everyone else! Guests who believe in the ritual above the common sense, may still opt to eat from the contaminated cake if they wish.

When we lived in small, rural communities with no mass transport and little international trade, germs were highly localized. Today, you can fly almost anywhere on the globe in less than 24 hours. People bring home exotic pathogens that have never before been seen in their families or neighborhoods, all the time. Doctors and hospitals have got the message; they constantly wash, and wear those blue gloves. Minimizing the ways we expose ourselves and others is only sane.