A condition doctors call vasomotor rhinitis produces a runny, stuffy, sneezy nose even when no true allergy or infection is present.
Many people are sensitive to things like perfume or dust, but a very common factor is cold, dry air.
Although the exact cause of vasomotor rhinitis is not known, doctors suspect it is chiefly the dryness rather than the coldness of winter air that makes it worse.
The colder air is, the less water vapor it can hold.
In people with the condition, blood engorges the nasal mucous membrane, sometimes turning it bright red or even purple.
The sufferer sneezes and drips away, but the mucus is clear, unlike the kind present in an infection. When the nose is very dry, receptors that lie under the nasal surface activate mucus production in the glands and vessels.
Treatment aims to relieve the symptoms and is not always satisfactory.
Humidified air may help, and some nose sprays may relieve the inflammation. Sometimes plain saltwater spray helps a sniffle.
However, patients should avoid drops and sprays that act as vasoconstrictors, narrowing the blood vessels in the nose, because they can cause a paradoxical effect, worsening the dilation of the blood vessels afterward.