“When warm, moist air from the lungs in the front section of the nose meets colder nasal walls and cold outside air, the water condenses,” explains Michael Soyka, senior physician in rhinology at the ear, nose and throat clinic at the University Hospital Zurich. This is a physical effect that also strikes when entering warm rooms in winter, when small water droplets form due to condensation on the surface of the glasses and block the view.
“In addition to this purely physical phenomenon, there are also specific nose phenomena,” says Soyka. Because the nose is a marvel in terms of its diverse functions: it humidifies the air we breathe in when it is too dry, cleans it and warms it up in winter. It extracts moisture from the exhaled air so as not to dehydrate itself too much, and it also has tissue in which the immune system is very active.
If you now move from a warm place to the freezing cold, it is a big challenge for the nose. She tries by all means to add moisture to the dry air. For this purpose, cold receptors in the nose report the cool temperature, which, under the influence of the parasympathetic nervous system, leads to an expansion of the blood vessels in the nasal mucosa. Soyka: “As a result, the erectile tissue swells and the contact surface between air and tissue increases; this can lead to a feeling of congestion.”
The increased blood flow also pushes more water into the inside of the nose. At the same time, glands in the nose are active, which also produce fluid. The nose is running. A study on skiers from Verona in 2001 showed that almost 50 percent of the 144 subjects developed a cold-induced runny nose.
In addition to this healthy reaction to external cold, there is also hypersensitivity, which is particularly common among allergy sufferers. Soyka reports: “The cold stimulus triggers a significantly more severe reaction in the nose with a feeling of congestion and a runny nose, sometimes even a burning sensation. Accordingly, these people react earlier and more strongly to the stimulus of dry, cold air.
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