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