why does looking at bright light make you sneeze?

[firetracie]

You know when you feel a sneeze coming on? It's cr@p when it just fizzles out without a reel 'sneeze'. A few years ago someone told me to look at a bright light to make the sneeze happen. And it works. Does anyone know why?

[Postdog]

I don't know, but at a guess I'd say when you are looking at the light, you close your eyes a little, and so move face muscles - maybe it's the movement of those muscles that does it.

I'll have to try that tho next time I have a dry sneeze.

[Postdog]

Well wouldn't you know!

I just had a potential sneeze, tried what you said, and it didn't have any effect whatsoever.

[SKA]

something to do with it activating hormones or cones and rods, I forgot should have paid more attention to biology in college!!
ask in the science section

[Clanad]

The Scientific American recently had an article on this phenomena... here's a pertinent excerpt: "...Reflexive sneezing induced by light, and sunlight in particular, is estimated to occur in 18 to 35 percent of the population and is known as the photic sneeze reflex (PSR) or the ACHOO (autosomal dominant compulsive helio-ophthalmic outbursts of sneezing) syndrome. Its genetic nature has been known for at least the last 25 years; it is periodically discussed in the medical literature and lay press. Observations that emerging from dim light into sunlight or turning to face directly into the sun commonly triggers the reflex prompted early inquiries into the trait. The number of induced sneezes--which seems to be genetically mediated and can be predicted within a family--is constant from episode to episode and typically numbers two or three... reports in publications oriented to military medicine have noted the potential danger to pilots experiencing the PSR. In fact, studies conducted by the military revealed that the PSR is not mediated by specific wavelengths of light and thus cannot be mitigated by the use of filtering lenses; rather the investigators concluded that the PSR is induced by changes in light intensity... "

[Sally]

Also thinking of pepper does it for me