Blowing out candles on cake can increase bacteria on icing by 1400%

Next time you blow out the candles on your birthday cake, make a wish for your good health, as scientists have found that the popular tradition causes bacteria on the icing to increase by 1,400 per cent.

Researchers from Clemson University in the US examined the potential spread of bacteria when blowing out candles on a birthday cake.

"The tradition of blowing out birthday candles has different theories as to its origin. Some theorise the practice began in Ancient Greece related to bringing cakes with lit candles to the temple of the goddess of the hunt, Artemis," researchers said in the study published in the Journal of Food Research.

"Other ancient cultures believed that the smoke from candles carried their wishes and prayers to the gods," they said.

This tradition has become commonplace in many parts of the world, they added.

They found that bioaerosols in human breath may be a source of bacteria transferred to cake surfaces.

To test aerosol transfer to cake, icing was spread evenly over foil and birthday candles were placed through the foil into a base. After consuming a pizza, volunteers were asked to extinguish the candles by blowing.

Researchers then recovered icing samples and determined the level of bacterial contamination.

Blowing out the candles over the icing surface resulted in 1,400 per cent more bacteria compared to icing not blown on, they found.