Chocolate with bacteria frosting: Study shows blowing out candles on cake spreads germs

WASHINGTON — What could ruin a perfectly delicious birthday cake?

How about germs?

A 2017 study in the Journal of Food Research found that blowing out candles over the icing surface resulted in 1,400 percent more bacteria compared to icing on a cake where no one blew out the candles.

Biological aerosols in the breath that is expelled from the mouth may be a source of bacteria.

So, when a person forcibly exhales, as with blowing out candles or sneezing, bacterial or viral particles in the respiratory tract could also be coming out.

The study cited some bacteria and viruses commonly found in respiratory aerosol, which include Staphylococcus, Streptococcus, Corynebacterium (which can cause diphtheria), Hemophilus (which can cause influenza), and Neisseria (which can cause meningitis).

Clemson University professor Paul Dawson, one of the authors of the study, told The Atlantic that festivities do not have to be ruined by someone’s germy breath on a birthday cake.

“It’s not a big health concern in my perspective,” Dawson said.

Mouths are normally full of bacteria, most of which aren’t harmful. However, he did say that he would probably avoid the cake if the candle-blower was clearly sick.

Perhaps one way to avoid the socially awkward situation of refusing cake because someone blew out the candles and you’re worried about germs is to have a separate cake for blowing out the candles, similarly to smash cakes for babies.

Or, maybe, just eat the cake.

Kristi King

Kristi King is a veteran reporter who has been working in the WTOP newsroom since 1990. She covers everything from breaking news to consumer concerns and the latest medical developments.


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