Their conclusion is that Rudolph's nose overheats. The team of scientists ran tests on reindeer to investigate. Video was released by the British Medical Journal.
They say Rudolph exerts so much energy pulling Santa's sleigh, that it overworks his nasal cooling mechanism.
The scientists say there could also be less likely reasons -- such as Rudolph has a chronic cold, a parasitic infection or perhaps is suffering from alcoholic intoxication.