What is the cause of the photic sneeze reflex?

18-35% of the human population are affected by a hereditary trait called the photic sneeze reflex, which causes them to sneeze when suddenly exposed to bright light. The phenomenon has been described as early as by Aristotle, but is poorly understood even today. A popular explanation consists in an interference of the ophthalmic nerve and the trigeminal nerve, but the details remain to be cleared up.

Thomas Jagau

Read more: http://www.scientificamerican.com/article.cfm?id=looking-at-the-sun-can-trigger-a-sneeze