Analysis of information sources in references of the Wikipedia article "Birthday cake" in English language version.
{{cite news}}: CS1 maint: multiple names: authors list (link)They then lit the candles and blew them out before diluting the frosting with sterilised water and spreading it out on agar plates for the bacteria to grow.
On average, blowing out the candles increased the amount of bacteria on the frosting by 14 times. But in one case, it increased the amount of bacteria by more than 120 times. "Some people blow on the cake and they don't transfer any bacteria. Whereas you have one or two people who really for whatever reason ... transfer a lot of bacteria." says Dawson."