Yes, blowing out birthday candles spreads bacteria.

That’s according to researchers from Clemson University in South Carolina in the U.S, who’ve determined that more than 2,000 “moisture particles” are exhaled when blowing out birthday candles.

Instead of baking real cakes, the researchers spread cake frosting on polystyrene wrapped in aluminium foil. Before blowing out the candles, they all ate pizza to get in a party mood.

“We also wanted to simulate a birthday party,” said study co-author Paul Dawson. “We thought it might help the salivary glands get going.”

The study, published in Journal Of Food Research, titled Bacterial Transfer Associated with Blowing Out Candles on a Birthday Cake, found that there was a lot of bacteria, but more surprisingly, that each blow resulted in different types of bacteria.


On average, blowing out the candles caused the frosting to grow 14 times as much bacteria. However, in one case, it was increased by more than 120 times, suggesting certain people transfer more bacteria than others.

Dr Dawson said he’s personally not too bothered by the findings. “In my opinion, you’re fine to eat a birthday cake if someone blew out the candles,” he explained. “I don’t think you’d get sick.”

Most of the germs in human mouths aren’t going to be a problem because most of them are not harmful.

On top of that, if blowing out candles on a birthday cake actually caused the spread of deadly diseases it would be obvious because of how common the practice is, especially in children.

Read also: 5 Bakery Cafe For The Fluffiest Bread

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