How and why do we sneeze?

We sneeze to clear irritating material from our upper air passages. This can be dust, pollen or snuff, or excess mucus blocking the nose when we have a cold or hay fever. Sneezing is a reflex action that blasts air out at up to 103mph to clear the air passages. Pain receptors in the cells lining the upper respiratory tract are triggered by the dust or mucus and instruct the medulla (the base of your brain) to make you sneeze.

The sneeze itself is just a very powerful out-breath. The vocal cords are kept shut till the pressure in the chest has risen, and then the air is suddenly allowed to escape upwards, being directed into the back of the nose by the soft palate. But the 103mph of a sneeze is nothing compared to the 600mph that a cough gets up to.