Have you ever sneezed when looking at the sun? Roughly 25 % of the human population has a condition that is known as Autosomal dominant Compelling Helio-Ophthalmic Outburst (shortened ACHOO) or the photic sneeze reflex, which basically means that the people with this condition have problems controlling their sneezing when looking at bright lights like the sun or directly into a light bulb.
I have this condition, and it is not really bothersome at all. I get the occasional sneeze when it’s very sunny outside and I’m looking at the direction of the sun, but in everyday-life this is definitely not a problem. It is inherited from your genes, so considering both my girlfriend and I have it, I am pretty sure I can expect my son to have it as well.
The sun, responsible for lots of sneezes in people with the dominant Compelling Helio-Ophthalmic Outburst. Image by Lykaestria at the English language Wikipedia, posted with the Creative Commons Attribution-Share Alike 3.0 Unported license.
The condition have been linked to a single-nucleotide polymorphism (SNP) on chromosome 2, which means that you only need one different nucleotide in the entire gene (at the correct spot of course) for this condition to be activated.
Anyway, let us take a closer look at what we think causes it.
What causes some people to sneeze when looking at bright lights
The exact cause is not entirely known, but the leading theory is that we think it might be linked to confusion of nerve signals. The optic nerve is closely located to the nerves in the nose, and triggering the nerves in the eyes might accidentally also trigger the nerves in the nose, which ends in a light-induced sneeze.
Research also show that the visual cortex might be more prone to over stimulation in people with the ACHOO condition, which is a step closer to understanding what exactly causes it, but we still don’t know for sure. The visual cortex is the part of the brain that is responsible for processing visual information, but the exact mechanism that happens when people have light-induced sneezes seems to still be unknown.
The end might have been a bit anticlimactic to most of you, but instead of thinking about it like another thing we don’t really understand, try to instead think about how many mysteries are left to be discovered about the human body. We are living in a really exciting time in terms of science, and I'm sure we will be able to read about research that finds the exact cause sometimes in the future! Thanks for reading, and leave a comment below if you got anything to share ;)
About the author
Hi, I’m 
I am very passionate about nature and biology, and have been studying ecology for a few years now. My passions are mostly within conservation biology, mycology (the studies of mushrooms), animal behavior and general microbiology. I really enjoy both the theoretical aspect, as well as the more practical aspect of biology, and I spend about as much time in front of biology textbooks as I do spend on finding and identifying plant, mushroom and animal species in the forests.
Make sure to hit the big follow button above to go to my profile and follow me! This will make sure all of my posts end up right in your feed, and you can get your daily dose of biology news without any hassle :)