A sudden expulsion of air through the NOSE, designed to expel irritating materials from the upper air passages. In sneezing, a powerful expiratory effort is made, the vocal cords (see VOICE AND SPEECH; LARYNX) being kept shut until the pressure in the chest has risen high. Air is then suddenly allowed to escape upwards, being directed into the back of the nose by the soft PALATE. One sneeze projects 10,000 to 100,000 droplets a distance of up to 10 metres at a rate of over 60 kilometres an hour. As such droplets may contain micro-organisms, it is clear what an important part sneezing plays in transmitting infections such as the COMMON COLD. Although usually transitory, sneezing may persist for days on end – up to 204 days have been recorded.

Sneezing may be caused by the presence of irritating particles in the nose, such as snuff or the pollen of grasses and flowers. It is also an early symptom of colds, INFLUENZA, MEASLES, and HAY FEVER, being then accompanied or followed by running at the nose (RHINITIS).