For the study, published in the Journal of Food Research , researchers made fake cake (because why waste a real one?) by frosting a circular piece of foil and sticking in some birthday candles. They then had "party-goers" who had just eaten pizza blow on the candles of some of the cakes, but not on others. Testing the frosting found that the cakes that had been blown on had massively more bacteria than the cakes that had not.