Why Does Bright Light Make Me Sneeze?

Do you, or someone you know, sneeze uncontrollably in response to bright light? This strange reflex is called Achoo Syndrome, also referred to as heliopthamolic outburst or photic sneeze reflex. Those with this dominant genetic trait, about 25% of the population, experience a paroxysm of sneezing when suddenly exposed to light. Because it is a dominant genetic trait, if even one of your parents pass the gene on to you, you will "Achoo."

Two Reflexes for the Price of One

Sneezing is a reflex action; muscles automatically responding to a stimulus without your consent. Sneezes usually occur when some type of irritant enters the nose. The pupillary light reflex is another automatic response, where the pupils of the eyes shrink when stimulated by a bright light.

Although it is known that Achoo Syndrome is genetically determined, scientists still don't fully understand this phenomenon. Any reflex, sneezing or pupils constricting, requires a message being sent through the nervous system; a stimulus is sensed, the message sent to the brain, and then the brain shoots a signal back to the body. Perhaps Achoo Syndrome is a mix-up of reflexes that results in an entirely unintended response.

Achoo Syndrome: Recently Understood, but Historically Ancient

Aristotle even made reference to the photic sneeze reflex in his Book XXXIII, section titled 'Problems concerning the nose,' In his writings, Aristotle mused: 'Why is it that one sneezes more after one has looked at the sun? Is it because the sun engenders heat and so causes movement, just as does tickling the nose with a feather?'

Photic Sneeze Reflex in Popular Culture

Achoo has also made its way into a childrens' classic. In the The Berenstain Bears Go to the Doctor, Papa Bear has a heliopthamolic outburst when taking the cubs to their pediatrician. He quickly reassures his family that he's not sick, 'It's just this bright sunlight.' Does a bear sneeze in the woods? Perhaps on sunny days.

Observing Achoo Syndrome in Action

If you want a front row seat to Achoo-palooza, stand outside a movie theater door that leads directly to the outdoors. You'll be surprised at the number of moviegoers who emerge from the dark theater into the bright sunlight and suddenly sneeze (often repeatedly). Now that you are in the know, you can explain the reason for the sneezin'.

Sources

Barnes, J. (1984) The Complete Works of Aristotle. Vol. 2. Princeton Univ. Press.

Berenstain, S. & Berenstain, J. (1981) The Berenstain Bears Go to the Doctor. Random House.

McKusick, V. (2003) Achoo Syndome, NCBI.

Thorpe, ed. (2004) Biology 120 Laboratory Manual. Grand Valley State University.