Sneezing is a natural human response to remove irritants from your nose. Although everyone sneezes, when and what causes your sneeze may be linked to your genetics, especially if you do so when exposed to bright light. This is called the photic sneeze reflex, which refers to the tendency to sneeze when moving from darkness to light.
Most of us have experienced a variety of sneezes—especially when allergy season or the common cold hits, or when our noses are irritated. Many of us might sneeze in response to an unexpectedly strong fragrance or nose tickle at some point in our lives.
Reacting to bright light through a sneeze is entirely different than your nose being directly impacted by an irritant.
Although the factors that cause the sneeze are different, the reaction is exactly the same.
A standard sneeze has no genetic links as literally everyone sneezes, but a photic sneeze reflex is not nearly as common and does have ties to your genetic makeup.
Let’s explore photic sneeze reflex in more detail, including its medical definition, cause, and possible tie to genetics.
What is a photic sneeze reflex?
By definition, photic sneeze reflex (PSR) is the uncontrollable reflex to sneeze when exposed to bright light. This condition affects 18% to 35% of the population and is most often brought on by direct exposure to bright sunlight after spending time in a dimly lit or dark space.
It is more formally (and humorously) referred to as the ACHOO syndrome, also known as the autosomal dominant compulsive helio-ophthalmic outbursts.
It is important to note that photic sneeze reflex is not directly caused by exposure to light but by a significant change in the intensity of light you are exposed to.
There is no formal treatment for this condition, but many individuals find that preparing ahead of time for sunlight exposure with hats or sunglasses helps reduce the involuntary reflex.
Risks
There are no known links between PSR and other negatively impactful health conditions.
It is not harmful to your health but can pose dangerous risks for those who may experience it while driving, flying, or operating motorized vehicles.
Causes
The actual cause of photic sneeze reflex is still unknown, but various studies have proven a direct link between PSR and genetics.
If one of your parents has PSR, you have a 50% chance of developing it yourself.
PSR has also been linked to a deviated septum in some individuals.
The Genetics Behind the Photic Sneeze Reflex
Many common human traits are often understood to have a genetic basis, yet only a few cases have identified influential genes.
Studies are scarce for the photic sneeze reflex, but it's been reported to be an inherited trait, meaning that you need only one mutated gene from your parents to show the condition.
Researchers conducted web-based participant-driven studies to investigate the genetic background of 22 common human traits, including photic sneeze reflex.1
No previous studies have reported genes associated with this particular reflex at the time of this study.
Data for these studies was collected within a research framework wherein research participants, derived from the customer base of 23andMe, Inc., a direct-to-consumer genetic information company, consented to the use of their data for research and were provided with access to their personal genetic information.
As for the photic sneeze reflex, participants were asked one question for this trait: ‘‘Do you tend to sneeze when exposed to bright sunlight?’’ Available answers were ‘‘Yes’’ and ‘‘No, what are you talking about?’’
People who responded that they did sneeze were treated as cases. Those who did not were treated as controls.
In total, 5,390 participants were genotyped.
They identified several SNPs (you can think of this as specific gene locations) that showed significant or potentially significant associations with photic sneeze reflex. 2
Of these SNPs two specific areas showed a tendency for photic sneeze reflex. One of the genes is observed in seizure-related syndromes. Therefore, there may be a link between photosensitive epileptic seizures and photic sneeze reflex (triggered by a sudden switch from being dark-adjusted to light), providing a possible link between this particular region of the chromosome and photic sneeze reflex.
Although the sample size of this study is relatively small, possibly due to an original, web-based, parallel design, this is the first study to identify SNPs associated with photic sneeze reflex.
Understand Your Risk of Photic Sneeze Reflex with Thorough Genetic Analysis
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Your genetic DNA testing results can reveal many answers to the questions about photic sneeze reflex or other health-related conditions.
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1 http://www.pubmed.ncbi.nlm.nih.gov/20585627/
2Among these, the C allele of rs4422110 (located on chromosome 2q22.3) near the Zinc Finger E-Box Binding Homeobox 2 (ZEB2) gene showed a tendency for photic sneeze reflex in this study population.
