Photic Sneeze Reflex: Understanding the Sun-Induced Sneezing

Have you ever stepped out into the bright sunlight and suddenly felt that unmistakable urge to sneeze? If so, you might be one of the 18-35% of the world’s population experiencing what is known as the photic sneeze reflex, a phenomenon where exposure to bright light causes one to sneeze.

This curious condition, also sometimes humorously referred to as the ACHOO syndrome (Autosomal Dominant Compelling Helioopthalmic Outburst), has puzzled scientists and laypeople alike for centuries¹.

One of the most intriguing aspects of this reflex is its apparent hereditability, suggesting a genetic component. Research indicates that people with the photic sneeze reflex tend to have family members who sneeze in sunlight, too. This has led scientists to speculate that the reflex could be autosomal dominant, meaning you only need to inherit the trait from one parent to experience it yourself possibly.((https://www.ncbi.nlm.nih.gov/books/NBK109193/))

The underlying mechanisms of why bright light triggers sneezing in some individuals are still not fully understood.((https://health.clevelandclinic.org/why-does-the-sun-cause-me-to-sneeze)) However, one theory is that it involves a mix-up in the brain’s signals. The optic nerve, which senses light entering the eyes, and the trigeminal nerve, which triggers sneezes, are situated closely together in the brain.

In some people, it’s believed that when the optic nerve sends a signal to the brain about bright light, the signal might accidentally cross paths with the trigeminal nerve, triggering a sneeze².

Despite its seemingly benign nature, the photic sneeze reflex can pose certain risks, particularly for individuals who require keen visual attention, such as driving. Those affected should wear polarized sunglasses or hats to minimize sun exposure.((https://www.healthline.com/health/photic-sneeze-reflex))

As researchers continue to unravel the mysteries of the photic sneeze reflex, our understanding of the human body’s complexities deepens. It underscores the wonders of biology and the importance of genetics in shaping our responses to the environment. This phenomenon serves as a reminder of the vast, unexplored territories within our own biology, urging us to keep questioning and exploring.

1. https://www.ncbi.nlm.nih.gov/gtr/conditions/C1863416/ [↩]
2. https://www.scientificamerican.com/article/why-does-bright-light-cau/ [↩]