Food Science

The Unsettling Truth About Blowing Out Candles on Cake

July 28, 2017

“Bacterial Transfer Associated with Blowing Out Candles on a Birthday Cake,” reads the title of a recent study out of the Journal of Food Research. That’s quite a headline! The study presented a somewhat unsurprising finding: Saliva travels, so, naturally, the seemingly benign act of blowing out candles on a birthday cake involves the transmission of bacteria.

To determine how much, exactly, bacteria gets transferred in this process, the researchers from Clemson University constructed a mock cake and simulated a meal-dessert sequence with their 11 test subjects, replicated 3 times on separate days. Their methodology involved taking a sheet of foil and cutting it in the shape of a circle, placing that foil on a Styrofoam disk, and enveloping it in a thin layer of Betty Crocker's Rich & Creamy Vanilla frosting. The researchers then planted 17 candles, evenly spaced, into the Styrofoam, careful to permeate both the icing and foil layers.

Each subject then smelled and consumed a slice of hot, piping pizza, meant to emulate a meal-dessert sequence. After lighting the candles on the mock cake, researchers asked subjects to blow until they doused the tiny flames. This was followed, of course, by a control scenario, which replicated the procedure except for the final step: The candles weren’t blown out.

Following each scenario, the researchers removed the candles from the Styrofoam bases without touching the icing. Using sterile forceps, they placed the folded foil in stomacher bags, pouring a bit of sterile peptone solution into the bags. They then spread the resultant solution on agar plates, where bacteria could blossom.

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The findings, ultimately, were that blowing out candles resulted in a whopping 15 times more the amount of bacteria, on average, recovered from the icing compared to the control samples. This number obviously varied from trial to trial and subject to subject; in one person's case, this number was as high as 120 times more.

None of this is terribly shocking. I don’t think the researchers quite mean to cause alarm, nor do they intend for this to give rise to the same germaphobic anxiety that's ruined bobbing for apples, double dipping, or sharing straws. “Bacterias are an unavoidable part of life, present in and on almost everything humans contact,” it concludes. No kidding!

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Top Comment:
“Isn't this comment almost funny now? Who'da thought?”
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What I find more interesting about this study is the potential it’s opening up for innovators to make this gesture germ-proof. These findings, the researchers hope, will simply arm people with more “awareness" of possible health risks associated with birthday celebrations, and prompt people to take steps toward preventing the spread of bacteria. There are signs that it's happening: The Atlantic's Sarah Zhang found a 9-year-old patent floating around out there for a sanitary birthday cake and candle cover system. Perhaps you may consider such a contraption totally unnecessary. But if it takes a cover system to ease people’s fears while preserving the pleasure of this ritual, so be it.

Read the study in full here. Do you blow out the candles on cakes? Let us know in the comments.


See what other Food52 readers are saying.

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Mayukh Sen is a James Beard Award-winning food and culture writer in New York. His writing has appeared in the New York Times, the New Yorker, Bon Appetit, and elsewhere. He won a 2018 James Beard Award in Journalism for his profile of Princess Pamela published on Food52.


Amy August 6, 2017
Once for a big Cub Scout banquet, we used air cannons to blow out the candles. They are just a piece of plastic covering the end of an open large plastic cylinder and they blow a huge blast of air to an amazing distance. It was the year of the H1N1 virus and everyone had been so sick. I couldn't stand the thought of the entire cub scout pack blowing out the candles on the huge sheet cake we had (it was for Cub Scouting's birthday, so naturally cake with candles). The boys loved it and the parents were amazed. Kind of a fun science project. For a larger air cannon, you could get a smoke machine and fill it to make giant smoke rings that blow out the candles. More of a visual impact.
Rhonda35 August 6, 2017
Love this! I'm not a germaphobe, per se, yet I've always wondered about this. Especially after having a child and attending dozens upon dozens of birthday parties where the celebrated child can barely keep his/her sh*t together, let alone produce a spit-free candle-blowing air current! (I've been to a fair amount of adult birthday parties with similar outcomes - lol!) I've never been a fan of frosting anyway, so the solution is easy for me; still, I find this study interesting. Thanks, Mayukh!
Tess August 4, 2017
Enjoy the slice of birthday cake whether you're a germphobic or not. If a few spittles won't bother you, that's just more icing to indulge in. For us germaphobics, just don't eat the top layer of icing.
Shalini August 4, 2017
Well, Mayukh, I'm a germaphobe and sooo happy you wrote this. Actually, I'm immunosuppressed with two children, so my hypochondria is warranted.
Your article brings up an interesting point. It's my littlest one's first birthday tomorrow, and now I can avoid the tradition some people insist on of having the birthday person be "helped" to blow out the candles by all attending children. Disgusting! I'll have my strawberry buttercream cupcake with a sude of your child's streptococcus A!
In all seriousness, thank you!
Shalini August 4, 2017
Suza August 3, 2017
"Each subject then smelled and consumed a slice of hot, piping pizza, meant to emulate a..." maybe meant "slice of piping hot pizza"? Always better to have fewer commas.
Shalini August 4, 2017
I actually love commas! Serially.
Janet R. August 3, 2017
So, After a couple of hundred years we are all going to dye from eating Birthday cake, how stupid is this article ???????? Like in all situations no matter what you do , KNOW YOUR SURROUNDINGS !
Suza August 3, 2017
Eoliver August 3, 2017
Or you put out the candles by swooping your hands up from near the sides of the cake and clapping them together just over it. It's actually pretty easy, once you get the hang of it, and much more dramatic! (And one of my favourite memories is my elderly mother putting out all 80 of her birthday candles in one swoop. After which she said "well, I've had years of practice.")
Margaret L. August 4, 2017
This sounds so fun -- I will be practicing!
Rhonda35 August 6, 2017
I have never heard of this method - anxious to try - off to bake a cake! ;-)
ellicia August 3, 2017
There was a funny episode of The Bernie Mac Show about this very situation. And yes, Bernie did get sick from his son's contaminated birthday cake. At the end he was questioning who came up with the idea of putting candles on a cake and then blowing them out in the first place. I always scrape off the icing, just in case.
Linda L. August 3, 2017
People have survived over many many years (forever) blowing out candles on their cakes ... and kids love this tradition. I find it sad that this is just another thing that 'do gooders' are screwing up for others enjoyment :(
DC August 3, 2017
We make a jumbo cupcake for the birthday person to have their candles. But I love the sparklers idea too! We have 4 winter birthdays in our house and many times there is colds/coughs going on so this is a good point, however, I don't think we should all freak out about germs in general except for the high school and college crowd, since STD's are so rampant.
DC August 3, 2017
We make a jumbo cupcake for the birthday person to have their candles. But I love the sparklers idea too! We have 4 winter birthdays in our house and many times there is colds/coughs going on so this is a good point, however, I don't think we should all freak out about germs in general except for the high school and college crowd, since STD's are so rampant.
Mildred M. August 3, 2017
Hello... I love making Birthday cakes for my Family and Friends.
But I have elevated the excitement to the new candle that you do not blow out and everyone is wowed. It is more exciting and no one misses all the germs. I am a germ phoebe, sorry. But I still know how to have fun with Birthdays, just use sparklers.
Pisanella August 3, 2017
lets all walk around with face masks on so we don't breathe each other's air while we're at it! And what's with the "are you channeling your best self with this comment" business?
Kristen M. August 3, 2017
We thought it was a good time to post our Code of Conduct with a handy reminder near the comment box, because the Food52 community works best—and is a whole lot more fun—when we all talk to each other in the comments with as much respect as we would in real life (wouldn't the rest of the internet be a nicer place if we all agreed to do that?). If you want to know more, check out the full Code of Conduct here:
carol August 4, 2017
thank you for the reminder - if you wouldn't say it in person you probably don't need to post it including the grammar shaming.
Rhonda35 August 6, 2017
Kudos, Kristen, for the Code of Conduct reminder! Food52 has always had such a lovely, welcoming community and I think the nudge to "channel our best selves" helps maintain it as such.
Isn't this comment almost funny now? Who'da thought?
carol August 3, 2017
really?! this is ludicrous. more opportunity to waste precious time,resources, etc. on non-issues. geez. blow away, i say. : )
Matt July 29, 2017
This assumes that you're sharing your birthday cake with others… my birthday cake is mine