Researchers from Clemson looked at this topic and published in the Journal of Food Research. Their research shows that blowing out candles on a birthday cake does deposit bacteria onto the cake. They found that blowing out candles on a cake increased the amount of bacteria on the cake’s frosting by 14 times.
This however does not necessarily make you 14 times more likely to get sick from eating the birthday cake. It really depends upon the type of bacteria.
In an article in The Atlantic www.theatlantic.com (July 2017) even the lead author of this study, Dr. Paul Dawson, Professor of Food Safety at Clemson, says that he doesn’t think bacteria from blowing out birthday candles is a big health concern and your chance of getting sick from a birthday cake is probably very minimal. So breathe easy.
The handling of the cake itself is probably riskier than the candle blowing. Did the person decorating or cutting the cake use standard safe food procedures? Did they wash their hands before handling the cake after using the rest room? Perhaps that person was sick when they were decorating the cake. Did they lick frosting off their fingers and then go back to decorating? Or was there accidental bacteria transfer from raw meat or poultry onto the cake? Things happen in kitchens, especially when people are rushed or feeding crowds that they aren’t used to doing.
A final word of caution: if you know the birthday celebrant is ill—give them their own personal cake with a candle and don’t share those germs with the other party goers.
Reference: Journal of Food Research, Vol 6, No 4 (2017) Bacterial Transfer Associated with Blowing Out Candles on a Birthday Cake
Cheryle Jones Syracuse, MS
Professor Emeritus, The Ohio State University
See our “Better Treats for Birthday” post here for 4 scrumptious desserts that are easier and better than cake especially for school classrooms.