The medical term for “runny nose” or nasal discharge is rhinorrhoea.
It is the excessive production of secretions that run out the front of the nose or back down the throat, especially when lying down. The appearance of the mucus can be clear and transparent or purulent and thick.
Rhinorrhoea is most often caused by rhinitis. Rhinitis is an inflammation of the nasal mucosa. The nasal mucosa reacts by secreting fluid and can often swell up, blocking the passage of air through the nose.
There are two types of rhinitis: acute rhinitis and chronic rhinitis. Allergic rhinitis is a kind of chronic rhinitis.
There is also vasomotor rhinitis, which occurs due to variations in temperature or humidity, due to smoke, dust or strong smells from chemical products or as a reaction to a medicine or hormonal changes.
A cold, or rhinopharyngitis, is a special form of infectious rhinitis caused by a viral condition.
Distinguishing between a simple cold and an allergy is often tricky, but certain characteristics can make it possible to determine between them:
Allergic rhinitis is the body’s exaggerated response to allergens. This response causes, among other things, the release of histamine, causing the swelling of the respiratory mucosa and the dilation of blood vessels. This dilation causes nasal congestion, overproduction of mucus and therefore rhinorrhoea.
Allergic rhinitis can be seasonal or persistent. In the first case, it occurs periodically, generally in the spring and summer, with the flowering of the plant responsible for the allergy. This is often called hay fever.
Persistent rhinitis is mostly caused by allergenic substances in the environment of the person in question. He or she seems to always have a cold. The episode is often triggered when waking up and can be repeated several times per day.
To find out more: Symptoms of dust mite allergy