Photic sneeze reflex
Sneezing is a natural response that removes irritants from your nose. But while it’s common to sneeze with a cold or allergies, some people also sneeze when exposed to bright light and other stimuli.
What is photic sneeze reflex?
Photic sneeze reflex is a reflexive sneezing induced by light, and sunlight in particular. It is estimated to occur in 18 to 35 percent of the population and is known as the photic sneeze reflex (PSR) or the ACHOO (autosomal dominant compulsive helio-ophthalmic outbursts of sneezing) syndrome.
Its genetic nature has been known for at least the last 25 years; it is periodically discussed in the medical literature and lay press. Observations that emerging from dim light into sunlight or turning to face directly into the sun commonly triggers the reflex prompted early inquiries into the trait.
How do genetics affect photic sneeze reflex?
Photic sneeze reflex is an inherited, genetic trait. But since sneezing is a regular occurrence, it’s possible to have this trait without realizing it. It’s also a dominant trait. If one of your parents has this reflex, you have a 50 percent chance of inheriting PSR or ACHOO syndrome, too.
The gene responsible for photic sneezing hasn’t been identified. But if you have the trait, you’ll likely sneeze multiple times in response to bright light. The number of sneezes could be as little as two or three, but some people report as many as 40 or more successive sneezes. The way the reflex manifests in you might differ from those in your family.
It’s important to note that while bright light can bring on ACHOO syndrome, the reflex isn’t trigged by light itself, but by a change in light intensity.
Sitting in a brightly lit house might not trigger a sneeze. But you may start sneezing if you step into direct sunlight. Similarly, if you’re driving through a tunnel on a bright, sunny day, you might start sneezing upon exiting the tunnel.
Photic sneeze reflex SNPS
It could be that single nucleotide polymorphisms, or SNPs, is the reason why photic sneeze reflex happen. In 2010, a group of geneticists identified two single nucleotide polymorphisms, or SNPs, that were associated with the sunny sneeze by assessing the genotypes of nearly 10,000 individuals.
These SNPs are alterations to single letters within a person’s genetic library. One is called rs10427255 and the other, about which there is somewhat less statistical certainty, is called rs11856995. One of them is located nearby a gene known to be involved in light-induced epileptic seizures, which raises the possibility that there might be some kind of biological link between the two syndromes.
Causes of photic sneeze reflex
The actual cause of photic sneeze reflex is unknown and the way in which sneezing is triggered is not very well understood, but there are several theories that attempt to explain the syndrome.
One theory is that sneezing involves the optic nerve. A change in light may stimulate this nerve, creating the same sensation as having an irritant in the nose. This sensation could possibly be responsible for the sneeze.
Another theory is that light exposure causes eye tears, which briefly empty into the nose. This might also cause temporary irritation in the nose and sneezing.
It’s not only a change in light that can trigger the sneeze reflex. Some people with photic sneeze reflex are also sensitive to other types of stimuli.
For example, if you have a history of photic sneeze reflex, receiving an eye injection — such as anaesthesia prior to eye surgery — may trigger a sneeze or two.
This is because an eye injection can stimulate the trigeminal nerve. This nerve provides sensation to your face, and it also signals the brain to sneeze.
There is also one theory say, that people who have the ACHOO syndrome have a hypersensitive reaction to light, just like some people have a sensitivity to cat hairs or pollen. When a person with the syndrome is exposed to a bright light, the same mechanism in the body that triggers a sneeze due to an irritant such as pollen somehow confuses light with that irritant and causes a sneeze to occur. Another idea is that the sneeze reflex in people with the ACHOO syndrome is somehow linked to real nasal allergies, although this does not explain the syndrome in people without nasal allergies. A different theory is that people with the ACHOO syndrome are very sensitive to seeing bright light. The sneeze reflex of the syndrome can then be thought of as an involuntary defense reaction against bright light; when the person sneezes, they automatically close their eyes.
Photic sneeze reflex symptoms and signs
Photic sneeze reflex (PSR) or Autosomal Dominant Compelling Helioopthalmic Outburst (ACHOO) Syndrome is characterized by uncontrollable sneezing in response to the sudden exposure to bright light, typically intense sunlight. About one in four individuals who already have a prickling sensation in their nose will sneeze in response to sunlight, but “pure” photic sneezing is far less common
Photic sneeze reflex treatment
Photic sneezing in it self isn’t harmful to your health. It’s a known condition, yet there aren’t any medications or surgical procedures to stop the reflex.
To avoid sneezing, some people shield their eyes before exposure to the sun and other bright lights by wearing sunglasses, scarves, or even a hat.
While photic sneezing isn’t related to allergies, taking an over-the-counter antihistamine may reduce the reflex in people who have seasonal allergies.
Photic sneeze reflex risks
Photic sneeze reflex can be dangerous in some situations, such as when operating a car or other motor vehicle. Sudden exposure to bright light could trigger successive sneezing, affecting your ability to maintain control of a car.
Because sneezing causes involuntary eye closure, multiple sneezes while driving could cause a traffic accident. Photic sneeze reflex can also pose a danger to airplane pilots.
If an eye injection triggers a sneeze reflex, you may start sneezing as a doctor injects medicine into your eye before surgery or another procedure. If the needle isn’t removed in time, you may have permanent or temporary eye damage.
If you have photic sneeze reflex and have concerns about these risks, talk to your doctor about how to minimize them.
Management of photic sneeze reflex
While this phenomenon is poorly understood, recent research has shown that antihistamines being used to treat rhinitis due to seasonal allergies may also reduce the occurrence of photic sneezes in people affected by both conditions.
Those affected by photic sneezing may find relief by shielding their eyes and/or faces with hats, scarves, and sunglasses,or by applying transverse pressure on the philtrum with their finger.
Photic sneeze reflex diagnosis/testing
The ACHOO syndrome is diagnosed simply by observing the sneezing pattern of a person, and by looking into the sneezing patterns of the person’s close relatives. If the person seems to sneeze every time they are exposed to a bright light, and if their parents and offspring do the same, then the diagnosis of the ACHOO syndrome can be made.
Currently, there are no known blood tests or other medical tests that can help diagnose the syndrome.
Photic sneeze reflex prognosis
People with the ACHOO syndrome generally have the condition for life. There is no evidence showing that the ACHOO syndrome in any way affects a person’s life span.
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