A sneeze can send air out of your nose at a remarkable speed.

The longer version

A sneeze begins as an irritation signal from the lining of the nose, triggered by dust, pollen, cold air or a tickle of the nerve endings there. The signal reaches a control centre in the brain stem, which coordinates a single reflex: a deep breath in, a closing of the throat and mouth, then a sudden release.

Chest and abdominal muscles contract together, forcing air out under pressure through the narrow nasal passages. Narrow openings speed up whatever flows through them, so the escaping stream travels far faster than normal breathing ever does. The whole sequence is automatic and difficult to interrupt once it has started.

Where this entry sits

These facts look at how the human body works in ordinary moments, from breathing and blinking to balance and sleep. They focus on anatomy, senses, and small reactions that happen constantly without any conscious effort. The full list sits on the Human Body page, where every entry is listed in order.