This is definitely one of those things that you don’t learn in medical school, and we were amazed when we found out that there was a real answer to this question.
Yes, some people do sneeze when they look at the sun. This is due to something called the photic sneeze reflex. It is also known as autosomal dominant compelling helio-ophthalmic outburst or ACHOO, solar sneezing, and photosternutatory reflex. The photic sneeze reflex usually causes more than one sneeze. A study of six Spanish families showed that sneezes occur with a frequency of two to three sneezes per sneezing episode, with about three seconds between each sneeze. The photic sneeze reflex occurs in approximately 10 to 25 percent of the population, but even sun-sneezers don’t do it all the time.
This reflex is not completely understood, but it is thought to occur due to an accidental crossing of nerve signals in the fifth cranial nerve nucleus. This reflex trait is genetic and is passed on in an autosomal dominant manner. That means that if one of your parents is a sun-sneezer, you have a 50 percent chance of being a sun-sneezer too.
If you read the journal Military Medicine, you might also know that the photic sneeze reflex is also considered a risk factor to combat pilots.
By Mark Leyner
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"Why do you sneeze when you stare at the sun?" was posted on Thursday, November 15th, 2007 at 12:29 am.