why do i sneeze when i look at the sun

Sneezing when looking at the sun is due to a condition called the photic sneeze reflex, or ACHOO syndrome (Autosomal Dominant Compelling Helio- Ophthalmic Outburst Syndrome). This reflex causes some people to sneeze when exposed to bright light, particularly when moving from a darker environment into bright sunlight. It happens because of a crossed wiring between the optic nerve, which senses bright light, and the trigeminal nerve, which controls sneezing. When bright light hits the eyes, the overstimulation of the optic nerve accidentally triggers the trigeminal nerve, causing a sneeze. This phenomenon is genetic and affects about 15-35% of people. It is harmless but can be an unexpected reaction to sunlight or other bright lights.