Day breaks on a springtime landscape. Bees gently buzz, birds sweetly chirp, and people… are violently sneezing. But it’s not the pollen in the air that’s causing this cacophony of coughing — it’s the sunlight itself. For a significant number of people (estimated at 15-30% of the population), sudden exposure to bright light triggers the sneeze response. Let’s find out why.
When can light makes you sneeze?
May 16 is the International Day of Light, commemorating the first successful operation of the laser by engineer and physicist Theodore Maiman in 1960. While artificial light such as lasers could trigger the sneeze response, sunlight is the typical culprit in causing the so-called solar, or photic, sneeze. This can occur in everyday situations, like when moving from a relatively dark office lobby to a sun-drenched sidewalk, or driving through a dimly lit tunnel and into the bright sunlight beyond. A sneeze or series of sneezes — some people report sneezing up to 40 times consecutively — triggered by light exposure is known as the photic sneeze reflex (PSR). Another more creative name for it is ACHOO syndrome, which stands for Autosomal Dominant Compelling Helioopthalmic Outburst syndrome.
The content in this post is from Primal’s 3D Atlas module. To learn more about this or other Primal learning resources, please fill in the form here and our team will be in touch.
Why do we sneeze?
Sneezing is the body’s way of clearing irritants from the nose. When things like pollen, small particles, smoke, or other matter enter the nostrils or nasal cavities, your body reacts automatically, contracting your muscles, squeezing your eyes shut, and forcefully blowing the irritant — along with microbes, mucus, and water — out through your nose and mouth.
What anatomy is involved in sneezing?
The act of sneezing involves more than just the nose and mouth. In a matter of seconds, signals received by the brain from the nose’s contact with irritants or from exposure to a difference in light intensity trigger different reactions throughout the body, causing some muscles and organs to contract and others to relax.
Anatomy involved in the act of sneezing includes the cranial nerves, the upper respiratory tract, the olfactory apparatus, and the eye. But it all starts with the nose.
More than just a protuberance, the nose is the external structure that houses the nasal cavity, nasal mucosa, and olfactory epithelium, the latter of which houses the main anatomical components of the olfactory system, responsible for our sense of smell.
Nose anatomy involved in sneezing includes:
- External nares – Another name for the nostrils, this is where air enters the nasal cavity.
- Nasal vestibule – A larger space inside each nostril, this area is lined by sweat, oil glands, and hairs, which filter out airborne particles.
- Nasal cavity – This large space located behind the nose is separated from the oral cavity by the hard and soft palates, and divided into left and right halves by the nasal septum.
- Nasal mucosa – Covering the walls of the nasal cavity, this highly vascular respiratory mucous membrane warms, moistens, and further filers the air.
- Olfactory epithelium – Located on the roof of the nasal cavity, this strip of mucous membrane houses millions of olfactory receptor cells that allow us to detect odors.
When the nasal vestibules and nasal mucosa are unable to filter out particles (or these areas become inflamed, as they do when certain viruses attack the body), they get irritated, sending a signal to the brain via the trigeminal nerve that it is time to clear out the nasal cavity by sneezing.
What is the ACHOO syndrome?
In PSR or ACHOO syndrome, the sneeze is initiated by light, rather than a physical irritant. Studies have shown that in ACHOO syndrome, sneezing is brought on not as a result of specific wavelengths of light, but by a change in light intensity like switching the light on in a dark room. ACHOO syndrome affects up to an estimated one-third of the population, mostly females, and is thought to be an inherited trait.
Although ACHOO syndrome was first described in 350 BC by Aristotle, the mechanisms behind the phenomenon remain unclear. Several theories have been suggested, including the optical-trigeminal summation theory, parasympathetic generalization theory, and hypersensitivity to visual stimuli in the visual cortex theory, but all require further research and validation.
Why does solar sneezing matter?
What if you’re one of the 15-30% of the population who uncontrollably sneezes when exposed to changes in light intensity? The good news is that in most cases, there’s no cause for worry. There is also no specific treatment for what is thought to be a genetically transmitted condition, inherited in an autosomal dominant manner. This means that if one of your parents has ACHOO syndrome, there is a 50% chance you will have it.
However, if you work as a combat pilot, are a Major League Baseball outfielder, drive professionally (especially in an area with tunnels), or work in any other profession where looking into the sun or bright light is part of the job, ACHOO syndrome could pose a safety risk by interrupting your vision and attention. To lessen the possibility of things going awry, try shielding your eyes with a brimmed hat or sunglasses. And don’t forget to bring it up with your doctor, who can investigate or rule out other possible causes.
The content in this post is from Primal’s 3D Atlas module. To learn more about this or other Primal learning resources, please fill in the form here and our team will be in touch.