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Posted by on Jul 11, 2011 in Research Blogging, Science | 2 comments

Who wants to see the baby sneeze?

That’s what my brother-in- law used to call out as he’d carry his infant daughter, a soft blanket draped over her face, out into the yard.  With that, all the little kids at my sister’s daycare would run over and gather around the baby. When they were all ready, my brother-in-law would whip off the blanket, the baby would squint her eyes in the bright sun, then, “Achoo!” “Achoo!” and the children would all break up laughing.


Why is this baby sneezing? (note, she’s not my niece mentioned above)

Lmao! Nooo nobody is as weird as u! RT @  I sneeze when I stare at the sun lol, anyone else do that? #random

About a quarter of you reading this know exactly what was going on there because it happens to you. You step out of the mall into a bright parking lot or you flip on the bathroom light in the middle of the night, and you get that tingly nose sensation, and “achoo!”

The rest of you might be surprised that there is such a thing as sneezing at bright light. Or you may have been a bit puzzled by those of us who sneeze so predictably at sudden bright light that we purposely stare at a light bulb or glance at the sun to induce an almost-sneeze to fruition.

I hate when I have to sneeze sooo desperately but the sun isn’t even out for me to look at for that emergency sneeze…


Brian uses sun sneezes to distract his stats class. Extra fun when they go outside!

A quick (and decidedly unscientific) glance at the Twitterverse tells me that there are three kinds of people: those who sneeze in response to bright light and assume that everyone has the power; those who sneeze and think they’re alone in their weirdness; and those who don’t have such a sneeze reflex and have never even heard of such a thing.

“The sun makes you sneeze? Are you, like, a reverse plant?”

So what’s the science behind this amazing hidden talent?

The sneezing phenomenon goes by a number of names: Photic Sneeze Reflex, Sun Sneeze, solar sneeze reflex, light sneeze reflex. It also carries the cutesy, but unwieldy, acronym, ACHOO (Autosomal Cholinergic Helio-Ophthalmologic Outburst) syndrome.  I’ve always called it Sunshine Sneeze.

The sunshine sneeze doesn’t happen all the time. It occurs when a sunshine sneezer’s eyes are accustomed to dark (or low light), and then are suddenly exposed to bright light. The change in light makes sneezer’s nose tingle and suddenly sneeze one or more times.

Photic sneeze reflex has been recognized at least since the time of Aristotle who postulated its cause thusly:

Q. Why does the heat of the sun provoke sneezing, and not the heat of the fire?

A. Because the heat of the sun doth dissolve, but not consume, and therefore the vapour dissolved is expelled by sneezing; but the heat of the fire doth dissolve and consume, and therefore doth rather hinder sneezing than provoke it.   

Well, not exactly, Aristotle. But good try.

Sun Sneeze is genetic
It’s an autosomal dominant genetic trait affecting about 25% of people of European ancestry.  Autosomal dominant means that only one parent has to have the ACHOO trait in order to pass the sneeze along and you only need one copy of the gene to exhibit the sneeze.  And, here’s something even more interesting: your genetics may determine how many times you sneeze!  (That’s something I didn’t know until just now, so am querying my family to see if they are 2-sneezers like I am.)  Some families report sneezing over 40 times! Obviously this would be a problem for drivers, airline pilots, and other professions that require close attention.


Sun sneezing for fun and profit: Kristy auditions for an allergy commercial

I don’t even have to open the curtains to know it’s sunny. If i wake up and sneeze about 40 times then the sun has got his hat on

Sun Sneeze is associated with a Single Nucleotide Polymorphism (also known as a SNP or snp (pronounced ‘snip’)) called rs10427255.  An SNP is a small part of a person’s DNA in which variations sometimes cause unique characteristics such as hair colour, the ability to detect certain scents, or, in this case, sneezes.

For rs10427255, a person will have one of the following allele combinations:  CC, CT, or TT.  Researchers at the genetic testing company 23andMe conducted an online survey of 5388 individuals of European ancestry and found that  each copy of the C version at rs10427255 increased a person’s odds of ACHOO by about 1.3 times.  They also found a suggestive association with rs11856995.

So genes determine the trait, but what causes the actual sneeze? That’s a good question.

you should develop sun sensitivity syndrome, you’ll never miss a sneeze again RT @____ I hate when i can’t sneeze and I want to.

A sneeze is a protective reflex, something out of our control.  You can tell this by how hard it is to stop a sneeze, especially one that comes on fast. You can also tell because it is impossible to spontaneously induce a sneeze. They just happen.

Don’t you hate when You gotta sneeze, and it won’t come out.”—–U POSE TO LOOK AT A LIGHT OR DA SUN AN U WILL LOL 😀

A normal sneeze is a multi-step event. First is the irritation phase, when something tickles your nose. That tickle excites the trigeminal nerve in your nose, which then sends a signal to the “sneeze center” of your brain, located in the medulla.  The sneeze center then sends a whole bunch of instructions causing your nose to water, your chest and throat muscles to contract, your eyes to shut, and finally, the sneeze to happen, exploding 2000 to 5000 fluid droplets into the air at 70 to 100 mph.

Not a lot of ppl kno this but if u look @ a bright light, then u’ll sneeze #TipOfTheDay #FACT!


Rylee says, “Bright Lights make me sneeze!”

So what is happening in a sunshine sneeze? People with sunshine sneeze usually react when they move suddenly from dark (or very low light) to bright light.  This may be related to another protective reflex – that of your pupils contracting to protect the eyes from being damaged by bright light.  And it may turn out that these two reflexes, in sunshine sneezers, are linked.

Ruth Tennen, of Stanford University, explains it this way:

In most people, these two reflexes — sneezing and pupil-shrinking — take different routes through the brain. But in sun-sneezers, there may be a mix-up. Shining a bright light on your eye also sends a message to your sneeze center, which tells you to sneeze. We know that there are lots of nerves packed really close together in your brain. In the case of sun sneezing, the wires (or nerves) are probably crossed just a bit.

And it’s not just sunlight that can trigger sneezing. Lots of sun-sneezers say that breathing in cold air, or tasting a strong flavor like mint gum, also makes them sneeze. This suggests that activating any nerve close to the trigeminal nerve-the one involved in sneezing-can cause the sneeze reflex.

Another theory called “parasympathetic generalization” postulates that activating one branch of the parasympathic nervous system, might cause a nearby branch to activate. In the case of sun sneeze, the bright light causes the person’s pupils to constrict and their eyes to water.  This might, in turn, cause neural generalization to lead to nasal congestion and a sneeze-inducing “tickling sensation.”


Sneeze in the sunshine and amaze your friends!

Another study posits that the sun sneeze may not be a classical reflex at all.  True reflexes occur at the brainstem (as in the case of regular sneezes) or in the spinal cord (such as the knee-tap reflex).  Using EEG, researchers at the Psychological Institute at the University of Zurich, have found some evidence that photic sneeze response may be a consequence of having a higher sensitivity to visual stimuli in the visual cortex.  Sudden bright light would cause visual overstimulation that would in turn cause a cascade of reactions that finally initiate a sneeze.

When I look into the sun it makes me sneeze does that mean I’m allergic?” no Travis. Bright lights cause humans to sneeze

In any case, my niece who sneezed for the daycare kids at the beginning of this post just emailed me back – she’s 22 now. She says: I have it… usually 2.. sometimes 3.. very rarely 4 sneezes.  The rest of my family weighed in remarkably consistent:  Dad, all three sisters, my daughter and ALL NINE of my nieces and nephews have it (plus 2 of 3 brothers-in-law).  And we are all 1-3 sneezers.  I’m pleased to say, that puts us in good company:

From "The Berenstain Bears go to the Doctor"

NOTE: 

All pull-quotes (except Aristotle and Ruth Tennen) are from Twitter (w/ user-names removed), collected July 7-8, 2011

Citations

ResearchBlogging.org
Eriksson, N., Macpherson, J., Tung, J., Hon, L., Naughton, B., Saxonov, S., Avey, L., Wojcicki, A., Pe’er, I., & Mountain, J. (2010). Web-Based, Participant-Driven Studies Yield Novel Genetic Associations for Common Traits PLoS Genetics, 6 (6) DOI: 10.1371/journal.pgen.1000993

Langer, N., Beeli, G., & Jäncke, L. (2010). When the Sun Prickles Your Nose: An EEG Study Identifying Neural Bases of Photic Sneezing PLoS ONE, 5 (2) DOI: 10.1371/journal.pone.0009208

2 Comments

  1. Great account of a fascinating phenomenon – at least for those of us who have it!

  2. It’s interesting to know that sun-sneezing is genetical. My mom is sun sneezer as well as my bro and me :). It’s possible that her grandchildren will by sun sneezers too 😮

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