Why looking at the light makes us sneeze

[klr]

Well, some of us anyway, including me:

If you find yourself sneezing when you come from the dark into the light, you’re not alone. Jason G Goldman investigates why this sudden syndrome strikes.

In 1991, a University of Manchester pathologist named Emyr Benbow wrote a letter to the editor of the British Journal of Ophthalmology. "Even trivial symptoms are more easily tolerated if you can put a name to them," he wrote, "even if that produces only an illusory understanding of their significance". The name he was referring to was "photic sneezing". Benbow suffered from a curious phenomenon where moving from darkness into very bright light, caused him to reflexively sneeze. He found it of some comfort that "it occurs in normal people".

The first formal investigation of the reflex was probably made in the early 1950s by a French researcher named Sedan. He discovered that some patients sneezed when he shined his ophthalmoscope, used to examine the retina, into their eyes. His continuing inquiry into six such photic sneezers established that they would also sneeze when exposed to bright sunlight, flash photography, and in one case, an ultraviolet light. In describing the phenomenon, he noted that the sneeze only occurs just as the patient becomes exposed to light; they don't continue to sneeze even if continually awash in the bright glow of the Sun (or an ophthalmoscope).

Since Sedan wasn't able to find any discussion of light-related sneezing in the medical literature, he concluded it must be quite rare. But by the time that physician H C Everett, who seems to have coined the phrase "photic sneeze reflex", wrote about it in the journal Neurology in 1964, it seems as if quite a bit more was known about the condition.

For one thing, it was known to be somewhat more common than Sedan had assumed. Researchers would go on to estimate that it afflicts some 17% to 35% of the world's population: some 23% of medical students in Everett's study, and 24% of blood donors in another.

The tendency of some people to sneeze in response to bright light wasn't only just noticed in the last century; the Greek philosopher and scientist Aristotle observed the phenomenon as well. In his Book of Problems, he (or possibly his students) asked, "why does the heat of the Sun provoke sneezing, and not the heat of the fire?" He concluded that the Sun's heat aerosolises the fluids within the nose, which triggers a sneeze. The heat of a fire, on the other hand, not only vaporises those fluids, but also consumes them, thus drying out the nose, which actually inhibits a sneeze.

Never mind that he wasn't exactly spot on either in the cause for the sunny sneeze – it's light, not heat – nor in the explanation, but it means that the reflex was known to some perhaps as early as the third century BC.

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continued at: http://www.bbc.com/future/story/2015062 ... -us-sneeze

[Brian Peacock]

Strange. When I go out into strong light I often come a bit. Perhaps this also happens to normal people?

[JimC]

Strange. When I go out into strong light I often come a bit. Perhaps this also happens to normal people?

There are no normal people on this forum...

[mistermack]

I find that I tend to singe my dick,

whenever I come into a bright light.

[cronus]

Can't go in the light. Have to stay in my internet linked coffin during the day. Also got no reflection in the mirror. Something wrong here....