In Brief

Blowing Out Birthday Candles Is Grosser Than You Think

Birthday cake
(Image credit: Africa Studio/Shutterstock)

It's hard to turn down birthday cake, but a new study might have you thinking twice about taking a slice — researchers found that blowing out birthday candles increases the amount of bacteria on the cake by 1,400 percent.

For the study, the researchers made faux birthday cakes — they frosted a circular piece of foil and placed it on top of a Styrofoam base, and put candles through the foil into the Styrofoam. Then, they tested the frosting for bacteria either after the candles were blown out, or when the candles weren't blown out. They used sterile water to dilute the frosting, and spread it on lab dishes to see how much bacteria grew.

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Rachael Rettner
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.