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Many people (perhaps a quarter of the population) sneeze when their eyes are exposed suddenly to bright lights, such as the sun. One place to observe this is outside a movie theater; 20-25% of moviegoers leaving the dark theater in the afternoon will sneeze within 15 seconds of walking into bright sunlight.

What causes this? It's not clear. It might have to do with "wires getting crossed", where nerve impulses travelling up the optic nerve cause a secondary discharge down the trigeminal nerve, which (in part) supplies sensory nerve fibers to the nasal mucosa. Another theory suggests that squinting squeezes the lacrimal sac, releasing tears down into the nasal cavity, which triggers the sneeze. Still another theory links the photic sneeze reflex to the autonomic nervous system.

Research has been done that indicates this is an inherited trait, transmitted in autosomal dominant fashion. It's also possible that photic sneezing is related to allergies. Some studies have shown that people whose allergies are in treatment are less likely to sneeze when exposed to light.

Other names for the photic sneeze reflex are:

  • Achoo Syndrome
  • Autosomal Dominant Compelling Helioophthalmic Outburst Syndrome
  • Sneezing From Light Exposure
  • Peroutka Sneeze
www3.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?100820
www.health.uab.edu/show.asp?durki=8319
www.pigdump.com/sept99/sept10.html
www.madsci.org/posts/archives/aug97/865380242.Me.r.html

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