The reason for Rudolph's luminous red nose has been a source of curiosity for thousands of years.
The question was bugging medical researchers in the US and the Netherlands so much that they decided to investigate.
Their research compared the noses of humans and the noses of reindeer and involved the use, for the first time, of hand-held video-imaging technology to get a really close-up look at how blood circulates in the nasal passages.
The scientists uncovered similarities between human and reindeer nasal microcirculation, but there was also an important difference: they found that the blood vessels and circulation networks inside the noses of reindeer are more tightly packed -- in fact 25pc denser -- than those of humans.
Nasal microcirculation plays important roles such as heating, filtering, and humidifying inhaled air, controlling inflammation, transporting fluid for mucous formation, and delivering oxygen.
They believe the differences explain why the nose of Rudolph, the lead flying reindeer employed by Santa Claus to pull his sleigh, is red and particularly suitable for this job.
"Rudolph's nose is red because it is richly supplied with red blood cells, comprises a highly dense microcirculation, and is anatomically and physiologically adapted for reindeer to carry out their flying duties for Santa Claus," they said.
They reported that the properties of Rudolph's legendary nose help to protect it from freezing during sleigh rides and to regulate the temperature of the brain".
"These factors are essential for flying reindeer pulling Santa Claus's sleigh under extreme temperatures," they said.
QThe findings of the study, 'Why Rudolph's nose is red' were considered so important that they were published in the prestigious 'British Medical Journal' in December 2012.
The research was carried out by scientists from Erasmus Medical Centre in Rotterdam, the Netherlands, and the University of Rochester in New York.