Various media outlets have been warning readers about the various unexpected places that germs like cold viruses and bacteria can be found: on a cellphone, the kitchen sink, and a toothbrush. Cake frosting can now find itself on that very list, because according to a study by food safety professor Paul Dawson, blowing out birthday candles can increase bacteria growth on the surface of cake icing by 1,400%.
Dawson conducted the study as a series around common questions regarding food safety. After preliminary tests showed that blowing on nutrient agar (edible sugar-based foods) may be a source of bacterial transfer, Dawson and his Clemson University students conducted a formal study in which the research objective was to “evaluate the level of bacterial transfer to top the of a cake after blowing out the candles”. Rather than using a real cake, they frosted a piece of foil over a cylindrical styrofoam base. In attempt to simulate an authentic birthday party, Dawson and his team had test subjects consume pizza in order to stimulate their salivary glands, then extinguish lit candles by blowing. This process was repeated multiple times Once the icing samples were sterilely recovered, they found that the bioaerosols in human breath led to a definitive increase in bacterial transfer. On average, the amount of bacteria on the frosting increased by 14 times. In one trial, it increased the number of bacteria by more than 120 times.
However, birthday cake lovers should not despair. Dawson says, “It’s not a big health concern in my perspective.” Human saliva is already abundant with bacteria, most of them harmless. If blowing out candles on birthday cakes posed a significant risk in the spread of bacterial diseases, it would be extremely apparent due to the popularity of the tradition. But if need be, especially paranoid germaphobes now have the option of “germ-proofing” birthday cakes with sanitary birthday cake covers especially equipped with holes for candles. So we can have our cake, and eat it too.