Buzz
When a sneeze is about to happen but refuses to emerge, you may have been told to gaze at a light. The idea is that it activates a reflex that prompts a sneeze, and surprisingly, this theory is rooted more in science than myth.
An estimated 17 to 35 percent of the population is prone to the photic sneeze reflex (PSR), commonly referred to as ACHOO (autosomal dominant compulsive helio-ophthalmic outbursts of sneezing) syndrome. PSR is sneezing triggered by light, especially sunlight. Scientists have been puzzled by this phenomenon for centuries. Aristotle once speculated that the heat from the sun touching the nose could cause sneezing. Two thousand years later, Francis Bacon tested this by walking into sunlight with his eyes closed and found that heat alone wasn't enough to induce sneezing. He theorized that the moisture from eye-watering due to light might flow into the nose and irritate it, causing sneezing. While this theory wasn’t far-fetched, current science suggests that the cause is more related to the brain rather than the nose.
Sneezing occurs when your brain's trigeminal nerve, which controls sensations and movements in your face, detects irritants like dust or hair inside your nose. This nerve is located near the optic nerve, responsible for vision. When the optic nerve detects a sudden shift from low to bright light, it causes the eye's pupils to constrict. In people with PSR, this signal is misunderstood by the trigeminal nerve, triggering a sneeze. The tendency to sneeze in response to light is inherited in an autosomal-dominant pattern, meaning the trait doesn't depend on the X or Y chromosome. If one parent has PSR, there’s a 50/50 chance that the child will inherit it as well.
While the ACHOO syndrome may seem amusing for various reasons, it can have serious consequences. A sneeze briefly interrupts vision, which can be hazardous for tightrope walkers, athletes, or even drivers with the condition. A 1993 article in the journal Military Medicine raised concerns that this phenomenon might be life-threatening for fighter pilots. Thankfully, it was later found that wearing a simple pair of sunglasses could prevent this issue.
