The Sneeze Center
A sneeze starts in the Medulla, a part of your brainstem. When the lining of your nose becomes irritated by dust, pollen, or germs, it sends an urgent message to this 'Sneeze Center.'
The brain then coordinates a massive group of muscles—including your chest, diaphragm, throat, and even your eyelids—to prepare for a blast.
The High-Speed Clear
The goal of a sneeze is to eject the irritant at maximum speed. A single sneeze can travel at 100 miles per hour (160 km/h) and send up to 40,000 tiny droplets into the air.
This powerful gust of wind clears the sensitive nasal passages much more effectively than a normal breath ever could.
The Photic Sneeze Reflex
Do you sneeze when you look at the sun? About 1 in 4 people have the Photic Sneeze Reflex. This happens because the nerve that detects bright light and the nerve that detects a tickle in the nose are very close together in the brain.
When the 'light' signal is very strong, it 'leaks' over to the 'nose' signal, and the brain thinks something is in your nose, triggering a sneeze.
The Eyes-Closed Rule
Your eyes snap shut during a sneeze due to an involuntary reflex. While many people think this is to prevent your eyes from 'popping out,' it's actually much simpler.