Blowing out birthday candles? Here’s how many germs end up on your dessert

A birthday cake isn’t complete without the candles, but new research suggests that when you blow them out, you’re spreading bacteria all over your dessert.

Scientists out of Clemson University in South Carolina say that on average, blowing out birthday cake candles increases bacteria counts on the icing of a cake by 14 times.

“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,” Dr. Paul Dawson, the study’s lead author, told the Atlantic.

In one example from the study, one volunteer’s blow increased the number of bacteria by more than 120 times.

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“Blowing out the candles over the icing surface resulted in 1,400 per cent more bacteria compared to icing not blown out. Due to the transfer of oral bacteria to icing by blowing out birthday candles, the transfer of bacteria and other microorganisms from the respiratory tract of a person blowing out candles to food consumed by others is likely,” Dawson wrote in his study.

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The quirky research included pizza and cake because the scientists wanted to simulate the feeling of a real birthday party. The pizza also got their salivary glands going.

After their pizza lunch, Dawson and his team put together a cake-shaped piece of Styrofoam, covered in icing and adorned with candles.

Then they took a deep breath and blew out the candles – they collected frosting and spread it out on agar plates to watch the bacteria grow.

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Bacteria counts increased 14 times more than icing that hadn’t been blown on, on average. The scientists carried out their tests three times on different days with 11 people in total.

Don’t worry, cake-lovers. Dawson said that while our mouths are covered in a microbiome of bacteria, our germs are safe for the most part. We’d know cake is a conduit for spreading disease by now if not, he 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 minimal,” Dawson told the Atlantic.

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The only time it may be worrisome is if the guest of honour blowing out the candles is sick.

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Dawson’s full findings were published in the Journal of Food Research.

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