The Health Reason Why You Might Want to Never Blow Out Birthday Candles Again

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Making a wish and blowing out the candles before digging into the cake is a birthday tradition so commonplace, it might seem rude if the guest of honor decides to skip it. But, the results of a new study show you might want to anyways—for the sake of your guests.

A study published in the Journal of Food Research investigated an idea that makes so much sense once you think about it: blowing on a cake might spread germs from the person’s mouth onto the icing. To explore the concept, researchers from Clemson University spread a layer of icing onto foil and placed birthday candles on top to recreate the scene. To stimulate saliva production (and fake a birthday party) participants were given a slice of pizza to eat, and then asked to blow out the candles. The frosting was then diluted with sterilized water and spread out on agar plates to allow any present bacteria to grow. 

The results were shocking. On average, blowing out the candles increased bacteria on the icing (and therefore your “birthday cake”) by 1,400 percent, an alarming 14 times, when compared to the frosting that wasn’t blown on at all. In one of the cases, blowing out the candles increased the amount of bacteria by 120 times.

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Paul Dawson, the study’s co-author and professor of food safety and Clemson, explained to The Atlantic that since conducting the study, he’s heard from people who have thought about this issue before he had, and have done quite impressive things to germ-proof the birthday party. The coolest thing he’s heard of: A patent exists for a sanitary birthday cake cover and candle system, which includes a cake holder and cover with holes for the candles. But, he also says that, unless you want to, it’s not totally necessary to pull out all the stops just yet.

“Some people blow on the cake and they don't transfer any bacteria, whereas you have one or two people who really for whatever reason...transfer a lot of bacteria.” Either way, Dawson explains that, in his opinion, this shouldn’t be a factor that ruins the celebration from now on. “It’s not a big health concern in my perspective,” he says. “In reality if you did this 100,000 times, then the chance of getting sick would probably be very minimal.” Your best bet is to avoid the cake if the candle-blower is clearly sick, but you hopefully knew that already.