Blowing out Birthday Candles Increases Cake Bacteria

It’s not a big health concern.


Putting birthday candles on a birthday cake is a tradition that has been around for a long time. For religious reasons, placing a large candle in the center of a cake symbolizes ‘the light of life.’

Although, there are various meanings behind placing candles on the cake. But according to a new study, blowing out birthday candles on the cake increases the number of bacteria on the cake by 1,400 percent.

To make things easy for the study, scientists experimented with an actual cake. They frosted a circular piece of foil, placed it on top of a Styrofoam base, and put candles through the foil into the Styrofoam.

But before blowing out the candles, the team ate a pizza, though it might help the salivary glands get going. They then tested frosting for bacteria either after the candles were blown out or when they weren’t blown out. Using sterile water, they diluted the frosting and then spread it out on lab dishes for bacteria to grow.

Scientists found that blowing out the candles on the cake resulted in 15 times more bacteria on the frosting. Each colony growing on the lab plate represents one original bacterial cell from the frosting.

Scientists noted, “Usually don’t need to be concerned about eating birthday cake after someone blows out the candles. That’s because, most of the time, these bacteria are not harmful.”

Paul Dawson, a professor of food safety at Clemson University in South Carolina, said, “It’s not a big health concern in my perspective. In reality, if you did this 100,000 times, then the chance of getting sick would probably be very minimal.”

“Our mouths are teeming with bacteria, most of them not harmful. If birthday cakes significantly contributed to the spread of deadly diseases, it’d be obvious by now given the ubiquity of the practice. We’d probably avoid the cake if the candle-blower were clearly sick, but that’s just common sense.”

Journal Reference

  1. Paul Dawson, Inyee Han, Danielle Lynn, Jenevieve Lackey, Johnson Baker, Rose Martinez-Dawson. Bacterial Transfer Associated with Blowing Out Candles on a Birthday Cake. Journal of Food Research Vol. 6, No. 4 (2017) DOI:10.5539/jfr.v6n4p1
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