Photic sneezing: genetic origin of sneezing when looking at the sun

photic sneezing

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What is photic sneezing?

Have you ever noticed if you sneeze when you come out of a tunnel or when you walk from a dark room into a sunlit room? If so, you may be suffering from what is known as photic sneezing.

Photic sneezing is an involuntary reaction of the body that occurs in people when they are exposed to bright, intense light, such as sunlight. It is estimated that this condition affects around 35% of the population. And that the number of successive sneezes people experience in each episode is usually between two or three, although in some cases it can be as many as 40.

Photic sneezing is not related to any seasonal or environmental allergy. Such as pollen allergy, nor does it occur as a consequence of a cold or flu.

Why does looking at the light make us sneeze?

First of all, it should be clarified that although bright light can trigger photic sneezing, it is not triggered by the light itself, but by a change in light intensity. It occurs when you suddenly move from a relatively dark place to a brightly lit place. For that reason, if you are a person with this reflex, you are likely to sneeze when you walk out of your front door on a sunny day, or when you emerge from a tunnel.

It is not known why humans have developed this reflex and whether it has any physiological relevance. The leading hypothesis suggests that it is an electrical process in which light stimulates the optic nerve causing that little tingle that makes you sneeze. What is known is that photic sneezing is an inheritable condition, with autosomal dominant genetics. It means that to have it you only need to inherit the gene responsible from one of your parents.

What kind of reflex is photic sneezing?

The photic sneeze reflex is usually not a major inconvenience for people who suffer from it, and does not in itself pose any health risks or require any treatment. However, the photic sneeze reflex may become dangerous in some specific situations, such as when driving a car. Sneezing causes us to close our eyes involuntarily, which can affect our ability to maintain control of a vehicle. In particular, photic sneezing can pose a considerable risk to airline pilots. For these professionals, learning to identify the situations that provoke it and how to anticipate them is of particular importance in order to successfully control the aircraft.

If you are one of those who suffer from photic sneezing, here are some simple tips that may help you to avoid sneezing:

  • Wear sunglasses, preferably polarised.
  • Use hats or caps to prevent sunlight from hitting your eyes sharply.
  • Try pinching your nose. Sometimes this method is useful to stop sneezing before it happens. When you feel the sneeze coming on, try pressing the top of your nose with your fingers, just above your eyes.
  • Use your tongue. Some people are able to stop a sneeze by pressing their tongue hard against their front teeth until the urge to sneeze passes.

Photic sneeze gene

Research into the photic reflex has found that a simple genetic variation may be responsible for determining whether or not a person will develop this peculiar trait. A genetic variation, also called a single nucleotide polymorphism (or SNP), involves the existence of a mutation in our DNA. In addition, it causes a different letter to appear at a particular place in our genetic code than expected. In relation to photic sneezing, studies have shown that having a C instead of a T in the genetic marker rs10427522 increases the predisposition to this type of reflex. Experts suggest that knowing more about the reasons and biological mechanisms involved in photic sneezing can help us gain a better understanding of human genetics and disorders such as photosensitive epilepsy.