Why do people sneeze when they look at the sun or a bright light?
About 25% of people will sneeze when they look at a bright light, or if they look at the sun. I am lucky enough to be one of those people and if anyone tells you it’s a myth, tell them to come stand in front of me on a sunny day. It’s called the Photic sneeze reflex, or ACHOO for Autosomal dominant Compelling Helio-Ophthalmic Outburst, we’ll call it sun-sneezing.
For the most part a person will have to have their eyes adjust to a bright light, so going from one brightly lit room to another will not cause the reflex, but going from a dark room to a bright room will cause the reflex. You’ll also not sneeze constantly when you’re out in bright sunlight either, although sometimes I think I’ll be sneezing forever.
The commonly believed cause of sun-sneezing is a malfunction in a nerve signal. A nerve called the trigeminal nerve is responsible for sneezes, and when the eyes adjust to bright light, the overstimulation of the optic nerve triggers the trigeminal nerve, and causes a sneeze, or many sneezes.