Sun sneezing is a real phenomenon and not just a myth.
The usual cause of a sneeze is an irritation or blockage in the nasal passages;
when we sneeze, air is forced from the nose and mouth to get rid of the irritant or blockage.
When we look at the sun, the increased intensity of light in our eyes
causes a high-frequency electrical signal to run through our optical nerves.
The neighboring nasal nerves pick up some of this signal
and send the message to the brain, triggering a sneeze.
It is a reflex similar to the one triggered by having an irritant
or blockage in the nasal passage.
Studies have shown that approximately 20% to 30% of people sneeze
when exposed to sunlight or other bright lights.
Sun sneezing can also be referred to as
"photic sneeze reflex"
or "Autosomal Dominant Compelling Helio-Ophthalmic Outburst Syndrome" (ACHOO Syndrome).
Cited from Reference.com - 02-18-2010
