Speaker 1: Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff,
Speaker 1: Lauren Vogelbomb here with a classic episode of the podcast.
Speaker 1: Today's delves into the weird nerve wiring in our faces
Speaker 1: that can make people sneeze even when nothing's bothering your
Speaker 1: nose at all. Rather, you've just seen a bright light.
Speaker 1: Hey brain Stuff, Lauren vogel Bomb here with today's question,
Speaker 1: why do some people sneeze when suddenly exposed to bright
Speaker 1: light like sunlight? Only about ten to thirty five percent
Speaker 1: of people do this. I happen to be one of them.
Speaker 1: And no, we're not allergic to the sun. We may
Speaker 1: be the proud owner of a photic sneeze reflex or PSR,
Speaker 1: also known as at Chew syndrome. And yes that's an acronym.
Speaker 2: It stands for autosomal dominant compulsive helio ophthalamic outbursts of sneezing.
Speaker 2: And don't worry, we'll get back to some of those
Speaker 2: terms in a minute. Been trying to figure out the
Speaker 2: cause of the photic sneeze for thousands of years. The
Speaker 2: ancient Greek philosopher Aristotle or an unknown author writing in
Speaker 2: his name, asked, why does the heat of the sun
Speaker 2: provoke sneezing and not the heat of the fire. Good question,
Speaker 2: Aristotle or fake. Aristotle's answer to himself was because the
Speaker 2: heat of the sun doth dissolve but not consume, and
Speaker 2: therefore the vapor dissolved is expelled by sneezing. So his
Speaker 2: theory is that the heat of the sun makes the
Speaker 2: inside of your nose wet, and you've got to purge
Speaker 2: that liquid with a good sneeze. M Fortunately, in the
Speaker 2: seventeenth century, the English science pioneer Francis Bacon decided to
Speaker 2: put Aristotle to the test.
Speaker 1: He showed that if a photic.
Speaker 2: Sneezer walks into the sun with his or her eyes closed,
Speaker 2: the reflex is not triggered. Therefore we know it's not
Speaker 2: caused by the heat. It's caused by your eyes reacting
Speaker 2: to light. So what do we know about the photic
Speaker 2: sneeze today. Well, one study in nineteen ninety three found
Speaker 2: that it's not any particular wavelength of light that causes
Speaker 2: the problem, So you can't protect against it by just
Speaker 2: filtering out red light or violet light or anything in between. Instead,
Speaker 2: it has to do with the intensity of the light.
Speaker 2: So the good news is that if you want to
Speaker 2: avoid the photic sneeze, there's a pretty easy solution that
Speaker 2: works most of the time. Plain old sunglasses.
Speaker 1: Also more good news.
Speaker 2: If you are one of these seventy to ninety percent
Speaker 2: of people listening and thinking, what on earth is she
Speaker 2: talking about? Am I going to catch this sneeze disease someday?
Speaker 2: You can rest easy. You can't acquire the photic sneeze
Speaker 2: reflex after birth. It's a genetic trait. A study in
Speaker 2: the nineteen sixties found that this trait is inherited through
Speaker 2: an autosomal dominant mechanism. This means that it doesn't matter
Speaker 2: which of your parents has the photic sneezing gene. If
Speaker 2: one of them has it, you have a fifty percent
Speaker 2: chance of being a photic sneezer yourself. But the question
Speaker 2: of why remains. No absolutely conclusive answer has been reached.
Speaker 2: But there's one very interesting theory. Photic sneezing happens because
Speaker 2: some wires are crossed your head. Normally, a sneeze is
Speaker 2: your nose's version of the passenger eject seat in James
Speaker 2: Bond's car. Sneezing begins when irritation in the nose is
Speaker 2: detected by an organ called the trigeminal nerve. When that
Speaker 2: nerve senses an unpleasant foreign substance, it sends the eject
Speaker 2: signal to the brain. But inside your head, this nerve
Speaker 2: runs very close to the optic nerve, which senses light
Speaker 2: in the eyes. So let's say the eyes of a
Speaker 2: photic sneezer are suddenly exposed to bright sunlight. The optic
Speaker 2: nerve detects this and sends another reflex signal ah to
Speaker 2: bright trink my pupils. But if the optic nerve runs
Speaker 2: a little too close to the trigeminal nerve, the pupil
Speaker 2: constriction signal also gets interpreted as a something's in my
Speaker 2: nose signal and Bam sneezing fit. Today's episode is based
Speaker 2: on a videoscript for houstuffworks dot Com written by Joe McCormick.
Speaker 2: Brain Stuff is production of iHeartRadio in partnership with how
Speaker 2: Stuffworks dot Com. It is produced by Tyler Klang. Four
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