Scientists say Rudolph's nose shines so brightly because it is richly supplied with red blood cells which help to protect it from freezing and to regulate brain temperature.
This superior 'nasal microcirculation' is essential for pulling Santa's sleigh under extreme temperatures, the 'Daily Mail' reported.
Tiny blood cells known as micro-vessels in the nose are vital for delivering oxygen, controlling inflammation, and regulating temperature, the scientists claim.
Norwegian and Dutch researchers knew how important this regulation is for flying reindeer, especially as they take to the skies from their frozen home near the North Pole.
They set out to test whether Rudolph's famous red nose was due to 'a highly dense and rich nasal microcirculation' compared with human noses.
Using a hand-held video microscope, they first assessed the noses of five healthy human volunteers and found a circulating blood vessel density of 15 mm/mm2.
When the technique was applied to two reindeer noses, the researchers found a 25 per cent higher density of blood vessels, carrying a super-rich concentration of red blood cells.
They also found a high density of mucous glands scattered throughout the reindeer noses, which they say helps 'maintain an optimal nasal climate during changing weather conditions and extremes of temperature as well as being responsible for fluid transport and acting as a barrier'.
Infrared thermal images showed that reindeer do indeed have red noses.
"The microcirculation of the nasal mucosa in reindeer is richly vascularised and 25 per cent denser than that in humans," said Professor Can Ince.
"These factors explain why the nose of Rudolph, the lead flying reindeer employed by Santa Claus to pull his sleigh, is red and well adapted to carrying out his duties in extreme temperatures," Can Ince said.
The study was published in the British Medical Journal.
