Why does the sun make a third of the population sneeze?

About one-third of the population experiences an intriguing phenomenon: the irresistible urge to sneeze when stepping out of a dark building into the bright sunlight. This reflex, known as the photic sneeze reflex, has fascinated scientists for centuries.


As early as 400 B.C., Aristotle pondered why exposure to the sun incited sneezing. More recently, this reflex, also called ACHOO syndrome (Autosomal Dominant Compelling Helio-Ophthalmic Outburst), has been identified as a dominant genetic trait. According to the National Center for Biotechnology Information, a person has a 50% chance of inheriting this reaction if one of their biological parents is affected.

The photic sneeze reflex often occurs with a sudden change in brightness, for example, when turning on a light in a dark room. Dr. David Lang from the Cleveland Clinic explains that it's not a specific wavelength but the intensity of light that triggers this reaction.

The frequency and intensity of this reflex vary from person to person. For some, it's an occasional phenomenon; for others, exposure to bright lights can cause repeated, uncontrollable sneezing, according to the Cleveland Clinic.

A study conducted in Alabama in 1995 showed that 33% of surveyed patients were affected by photic sneezing. More recently, research conducted in China in 2019 found that 25% of examined individuals exhibited this reaction. The exact mechanisms of this phenomenon are still unclear to researchers. The leading hypothesis is that intense light stimulates the trigeminal nerve, causing crossed signals between the branches leading to the eyes and the nose.

Genetic mutations related to photic sneezing were discovered in a 2010 study by biotech company 23andMe. Another study from 1995 suggested a link with nasal septum deviation, while Japanese research in 2019 proposed a possible association with migraines.

Photic sneezing is generally benign but can pose risks in dangerous situations, such as while driving. To manage it, wearing sunglasses is recommended. Dr. William Howland also advises pressing on the philtrum (the space between the bottom of the nose and the upper lip) to prevent this reaction, a technique validated by an Australian study in 2019.