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There’s Actually A Reason You Sneeze When You Look At Light

Props to whoever named it ACHOO.

Anthony Rivas
by Anthony Rivas

BuzzFeed News Reporter

Have you ever tried looking into a light (or the sun) to sneeze?

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Someone might have suggested it to you once after noticing that you were on the verge of sneezing, but couldn't quiiiite get it out. Did it work? Did it make you wonder how on earth looking at light — y'know, with your eyes! — could possibly make you sneeze? If you're like me and you never heard of this before, then chances are you thought this HAD TO BE a myth.

Well guess what y'all, I'm here to tell you now that this is not BS. It's legit. Go ahead, try it out and see if it works for you.

If it worked for you, then you might have what's known as photic sneeze reflex — although I prefer calling it by its other name, ACHOO.

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ACHOO actually stands for autosomal dominant compelling helioopthalmic outburst syndrome, and it's surprisingly common throughout the population, occurring in about one out of every four people.

Upon discovering this, I reached out to ear, nose, and throat specialists Dr. Roheen Raithatha, of ENT & Allergy Associates, LLP in New York City, and Dr. Abbas Anwar, of Southern California Head & Neck Medical Group, to learn about this random AF phenomena. Here's what they had to say about it.

It's definitely a trait that's passed down from one of your parents.

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ACHOO has been recognized for hundreds of years. In Aristotle's Book of Problems, he suggests that looking at the sun causes the moisture in the nose to evaporate, forcing us to sneeze.

It was a good guess, but since then, scientists have discovered that there's a genetic basis for the reflex. In most body cells, there are 23 pairs of chromosomes (you inherit one set from each parent). Only one of these pairs are the sex chromosomes, and the other 22 are what are known as autosomes. So the "autosomal dominant" in ACHOO means that it's a non-sex-linked dominant trait. "If one parent has it, there's a 50/50 chance that their children will have it," Raithatha tells BuzzFeed Health.

And while nobody knows exactly how it happens, there are a couple of theories. One of them is that it's caused by a glitch in one of the head's main nerves.

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That nerve is the trigeminal nerve, and it has three main branches, each of which extends to the upper, middle, or lower part of the head. With ACHOO, it's the top two branches — the ophthalmic and maxillary branches — that get crosswired, Anwar tells BuzzFeed Health. So even though it should only be the ophthalmic branch that reacts to bright light (which can be considered an irritant), the maxillary branch gets caught up in this reaction, too. It thinks there's an irritant in the nose, and triggers a sneeze.

Apparently, this sort of cross-wiring is common throughout the head, Anwar says. "Some people have sore throats and feel it in their ears...there’s so much cross-wiring going on with these nerves, and it’s such a tiny area."

The other theory is that it's caused by a quirk in your body's involuntary nervous system.

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Also known as the autonomic nervous system (ANS), this system is responsible for bodily functions that we cannot consciously influence. Within the ANS is the parasympathetic nervous system (PSNS), which might be where your ACHOO comes from. "Another theory is called parasympathetic generalization," Raithatha says. "That's when one portion of the PSNS gets activated, other parts of the same system can also be activated. So when a bright light causes a pupil of the eye to constrict, which is part of the PSNS, it may indirectly cause another portion of the PSNS to respond, which can cause secretions and congestion in the nasal mucous membranes, and can sometimes lead to a sneeze as well."

And yes, this can happen pretty quickly, he says. "It's why when people eat spicy foods, they can immediately get a runny nose."

The reflex is most often triggered by sudden exposure to bright light — like when coming out of a tunnel and seeing the sun — but really, it could probably be any light.

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"Historically, we talk about it being sunlight but in theory it can be any bright light," Raithatha says. "Scientists have actually elicited a response from people by shining a bright flashlight into the eyes of patients. Camera flashes can be a trigger as well, and that’s been shown."

People might also have variations of the response, he says. So while some people might only feel an itchiness in their nose after seeing a bright light, others might sneeze once, while others will have a full-on sneezing fit.

After you sneeze, there will usually be a period of time where looking at light will have little to no effect.

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It's called a refractory period, and it's a certain amount of time — anywhere from a few minutes to several hours, depending on the person — where looking at light won't really trigger the reflex. "It kind of fatigues itself for a while," Anwar says.

There's not much you can do to stop the reflex from happening, but being aware of it can help to reduce the effects it has.

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We don't hear about ACHOO too much because it's not really something that severely affects people's quality of life. "I’ve actually never seen a patient coming in specifically for that," says Anwar. But ACHOO can present certain dangers to people who are operating heavy machinery, like driving a car or piloting an aircraft, if it happens at an inopportune time, he says. "It can cause the driver to lose control of the vehicle," he says, noting that people can try to lessen the effect of the light by wearing sunglasses or hats.

If you have the reflex, then it might also be good to notify your doctor or dentist about it if you're getting any kind of procedure done around the eyes or mouth, especially if sharp instruments are involved, Raithatha says. "If someone knows they have a condition like this, where they’re triggered by bright light, they should certainly let their doctor know so that they can let their sneezing pass before the doctor proceeds with the procedure itself," he says.