Chow Line: Blowing Out Candles on Birthday Cake Is Gross to Some, But Not Dangerous

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I’ve always felt grossed out when people blow out the candles on birthday cake and then everyone else eats the cake. Am I wrong to feel that way? Doesn’t that spread germs?

Well, according to a recent study published in the Journal of Food Research, blowing out candles on a birthday cake does deposit bacteria onto the cake. The study found that on average, blowing out the candles on the cake increased the amount of bacteria on the cake’s frosting by 14 times.

To determine whether bacteria are transferred through blowing out candles, the study authors created a model birthday cake by placing foil covered with cake icing on top of a Styrofoam base and placing candles on top. Test subjects then ate pizza and blew out the candles. The foil icing samples were then tested to see how much, if any, bacteria was deposited, according to the study.

The results? The icing samples that were blown on were found to have on average 14 times the amount of bacteria as compared to the samples that were not blown on.

But, that doesn’t mean that people who eat the cake are 14 times more likely to become sick, says Abigail Snyder, an assistant professor and food safety field specialist in the College of Food, Agricultural, and Environmental Sciences (CFAES) at The Ohio State University.

That’s because the safety of foods is not based on the total number of bacteria found in the foods, she said. Rather, food safety is based on whether or not disease-causing bacteria, also caused pathogens, are transmitted to the food, Snyder said.

“Foodborne pathogens often contaminate food through the fecal-oral route, which is exactly what it sounds like,” she said. “So while some may find it gross that blowing on candles increases bacteria, it doesn’t necessarily represent a food safety hazard based on the identify of that bacteria.

“It would be more of a concern if someone were to handle the cake after going to the bathroom and didn’t wash his or her hands, or handled raw meat and then touched the cake without washing his or her hands.”

So, if you want to blow out the candles on your birthday cake, go right ahead.

And for those who prefer not to continue with that tradition, maybe you can use a cupcake with a number candle for the birthday boy or girl to blow out instead.

Chow Line is a service of the College of Food, Agricultural, and Environmental Sciences and its outreach and research arms, OSU Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Tracy Turner, 364 W. Lane Ave., Suite B120, Columbus, OH 43201, or

Editor: This column was edited by Abigail Snyder, an assistant professor and food safety field specialist for CFAES.

Tracy Turner
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Abigail Snyder
OSU Extension