1 00:00:01,840 --> 00:00:07,600 Speaker 1: Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff, 2 00:00:07,680 --> 00:00:10,959 Speaker 1: Lauren Vogelbomb here with a classic episode of the podcast. 3 00:00:11,640 --> 00:00:16,040 Speaker 1: Today's delves into the weird nerve wiring in our faces 4 00:00:16,200 --> 00:00:19,800 Speaker 1: that can make people sneeze even when nothing's bothering your 5 00:00:19,840 --> 00:00:25,040 Speaker 1: nose at all. Rather, you've just seen a bright light. 6 00:00:25,720 --> 00:00:28,480 Speaker 1: Hey brain Stuff, Lauren vogel Bomb here with today's question, 7 00:00:28,920 --> 00:00:32,400 Speaker 1: why do some people sneeze when suddenly exposed to bright 8 00:00:32,479 --> 00:00:36,280 Speaker 1: light like sunlight? Only about ten to thirty five percent 9 00:00:36,320 --> 00:00:38,640 Speaker 1: of people do this. I happen to be one of them. 10 00:00:39,000 --> 00:00:41,840 Speaker 1: And no, we're not allergic to the sun. We may 11 00:00:41,880 --> 00:00:45,400 Speaker 1: be the proud owner of a photic sneeze reflex or PSR, 12 00:00:45,800 --> 00:00:49,760 Speaker 1: also known as at Chew syndrome. And yes that's an acronym. 13 00:00:50,080 --> 00:00:55,320 Speaker 2: It stands for autosomal dominant compulsive helio ophthalamic outbursts of sneezing. 14 00:00:55,760 --> 00:00:57,639 Speaker 2: And don't worry, we'll get back to some of those 15 00:00:57,720 --> 00:01:01,280 Speaker 2: terms in a minute. Been trying to figure out the 16 00:01:01,360 --> 00:01:04,840 Speaker 2: cause of the photic sneeze for thousands of years. The 17 00:01:04,920 --> 00:01:08,400 Speaker 2: ancient Greek philosopher Aristotle or an unknown author writing in 18 00:01:08,400 --> 00:01:11,119 Speaker 2: his name, asked, why does the heat of the sun 19 00:01:11,200 --> 00:01:14,600 Speaker 2: provoke sneezing and not the heat of the fire. Good question, 20 00:01:15,080 --> 00:01:18,800 Speaker 2: Aristotle or fake. Aristotle's answer to himself was because the 21 00:01:18,840 --> 00:01:22,240 Speaker 2: heat of the sun doth dissolve but not consume, and 22 00:01:22,319 --> 00:01:27,160 Speaker 2: therefore the vapor dissolved is expelled by sneezing. So his 23 00:01:27,319 --> 00:01:29,560 Speaker 2: theory is that the heat of the sun makes the 24 00:01:29,560 --> 00:01:31,800 Speaker 2: inside of your nose wet, and you've got to purge 25 00:01:31,800 --> 00:01:35,600 Speaker 2: that liquid with a good sneeze. M Fortunately, in the 26 00:01:35,680 --> 00:01:39,360 Speaker 2: seventeenth century, the English science pioneer Francis Bacon decided to 27 00:01:39,360 --> 00:01:40,679 Speaker 2: put Aristotle to the test. 28 00:01:41,160 --> 00:01:42,560 Speaker 1: He showed that if a photic. 29 00:01:42,319 --> 00:01:45,039 Speaker 2: Sneezer walks into the sun with his or her eyes closed, 30 00:01:45,319 --> 00:01:48,440 Speaker 2: the reflex is not triggered. Therefore we know it's not 31 00:01:48,480 --> 00:01:51,440 Speaker 2: caused by the heat. It's caused by your eyes reacting 32 00:01:51,480 --> 00:01:54,080 Speaker 2: to light. So what do we know about the photic 33 00:01:54,160 --> 00:01:57,800 Speaker 2: sneeze today. Well, one study in nineteen ninety three found 34 00:01:57,880 --> 00:02:00,560 Speaker 2: that it's not any particular wavelength of light that causes 35 00:02:00,560 --> 00:02:03,160 Speaker 2: the problem, So you can't protect against it by just 36 00:02:03,240 --> 00:02:07,400 Speaker 2: filtering out red light or violet light or anything in between. Instead, 37 00:02:07,560 --> 00:02:09,720 Speaker 2: it has to do with the intensity of the light. 38 00:02:10,240 --> 00:02:12,040 Speaker 2: So the good news is that if you want to 39 00:02:12,040 --> 00:02:14,880 Speaker 2: avoid the photic sneeze, there's a pretty easy solution that 40 00:02:14,960 --> 00:02:17,760 Speaker 2: works most of the time. Plain old sunglasses. 41 00:02:18,400 --> 00:02:19,720 Speaker 1: Also more good news. 42 00:02:19,880 --> 00:02:21,919 Speaker 2: If you are one of these seventy to ninety percent 43 00:02:21,960 --> 00:02:24,720 Speaker 2: of people listening and thinking, what on earth is she 44 00:02:24,800 --> 00:02:28,160 Speaker 2: talking about? Am I going to catch this sneeze disease someday? 45 00:02:28,840 --> 00:02:31,639 Speaker 2: You can rest easy. You can't acquire the photic sneeze 46 00:02:31,680 --> 00:02:35,040 Speaker 2: reflex after birth. It's a genetic trait. A study in 47 00:02:35,080 --> 00:02:37,799 Speaker 2: the nineteen sixties found that this trait is inherited through 48 00:02:37,800 --> 00:02:41,560 Speaker 2: an autosomal dominant mechanism. This means that it doesn't matter 49 00:02:41,639 --> 00:02:44,720 Speaker 2: which of your parents has the photic sneezing gene. If 50 00:02:44,720 --> 00:02:46,799 Speaker 2: one of them has it, you have a fifty percent 51 00:02:46,880 --> 00:02:50,440 Speaker 2: chance of being a photic sneezer yourself. But the question 52 00:02:50,520 --> 00:02:54,600 Speaker 2: of why remains. No absolutely conclusive answer has been reached. 53 00:02:54,800 --> 00:02:58,760 Speaker 2: But there's one very interesting theory. Photic sneezing happens because 54 00:02:58,760 --> 00:03:02,200 Speaker 2: some wires are crossed your head. Normally, a sneeze is 55 00:03:02,240 --> 00:03:05,280 Speaker 2: your nose's version of the passenger eject seat in James 56 00:03:05,280 --> 00:03:08,880 Speaker 2: Bond's car. Sneezing begins when irritation in the nose is 57 00:03:08,919 --> 00:03:11,960 Speaker 2: detected by an organ called the trigeminal nerve. When that 58 00:03:12,000 --> 00:03:15,400 Speaker 2: nerve senses an unpleasant foreign substance, it sends the eject 59 00:03:15,400 --> 00:03:18,880 Speaker 2: signal to the brain. But inside your head, this nerve 60 00:03:18,960 --> 00:03:21,799 Speaker 2: runs very close to the optic nerve, which senses light 61 00:03:21,919 --> 00:03:24,680 Speaker 2: in the eyes. So let's say the eyes of a 62 00:03:24,680 --> 00:03:28,280 Speaker 2: photic sneezer are suddenly exposed to bright sunlight. The optic 63 00:03:28,320 --> 00:03:31,440 Speaker 2: nerve detects this and sends another reflex signal ah to 64 00:03:31,560 --> 00:03:35,080 Speaker 2: bright trink my pupils. But if the optic nerve runs 65 00:03:35,080 --> 00:03:37,720 Speaker 2: a little too close to the trigeminal nerve, the pupil 66 00:03:37,760 --> 00:03:41,040 Speaker 2: constriction signal also gets interpreted as a something's in my 67 00:03:41,120 --> 00:03:51,160 Speaker 2: nose signal and Bam sneezing fit. Today's episode is based 68 00:03:51,200 --> 00:03:54,560 Speaker 2: on a videoscript for houstuffworks dot Com written by Joe McCormick. 69 00:03:54,920 --> 00:03:57,480 Speaker 2: Brain Stuff is production of iHeartRadio in partnership with how 70 00:03:57,520 --> 00:04:00,440 Speaker 2: Stuffworks dot Com. It is produced by Tyler Klang. Four 71 00:04:00,520 --> 00:04:03,480 Speaker 2: more podcasts from my Heart Radio, visit the iHeartRadio app, 72 00:04:03,600 --> 00:04:06,520 Speaker 2: Apple Podcasts, or wherever you listen to your favorite shows.