If we go out into the cold in winter, it doesn’t take long and the nose starts to run. What many may find annoying makes perfect physiological sense, as Michael B. Soyka, head rhinologist at the University Hospital Zurich, explains: “The increased secretion of fluids at cool temperatures is due to the fact that the nose has to warm up the air we breathe.”
This happens via the so-called vasodilation – that is, via the widening of the blood vessels. This in turn leads to improved blood circulation and also to increased mucus production. Physical phenomena such as condensation also contribute to the formation of secretions.
This mucous film with all its proteins and mucins – these are protective substances in the nasal secretion – ensures that viruses and bacteria are more easily carried out of the nose. A mechanism that, by the way, also plays a role in warmer temperatures; only then it is less noticeable because the nose does not have to warm the air and therefore secretes less fluid. So that we inhale as few potentially harmful foreign substances as possible, the nose has already installed a first, coarse filter at its entrance: the nasal hair. They catch larger dust particles or even insects.
The nose works like an air conditioner
Further up, the cilia, which lie like a carpet on the mucous membrane, take over the fine filtering: With their constant fanning, they transport unwanted particles towards the throat, from where they can then be swallowed or spat out. “Our nose is actually an air conditioner marvel,” says ear, nose and throat specialist Soyka. “It humidifies the air we breathe if it is too dry, warms it up in winter, cleans it, releases molecules that widen the blood vessels and also has immunologically effective tissue.”
Nevertheless, our body’s own air purification system is reaching its limits, especially now in winter. Against aerosols – be they contaminated with flu viruses or with corona – even our noses are sometimes powerless. “Then only a mask and vaccinations protect, as we have all known since this pandemic,” says the specialist.