The tongue-in-cheek investigation, published by the British Medical Journal in its Christmas edition used a hand-held microscope to examine the nasal lining of five healthy humans, two reindeer and a sixth person with a non-cancerous nasal growth.

It is the first time a scientific explanation has been offered for the glow that allows the world’s most famous antlered herbivore to guide Santa’s sleigh through the night before Christmas.

The tiny blood vessels provide plentiful oxygen-carrying cells and help control the body’s temperature, showed their findings, which were backed by an infrared image of a reindeer after exercise.