The reason why some people sneeze when looking directly at the sun

Suddenly sneezing uncontrollably when walking outside from a dark space (movie theater, closed room, .), you should not be too worried. Because there are about 25-30% of the world's population also have a similar situation, and scientists give it a name, called: light sneezing reflex.

Why look straight at the sun that some people sneeze?

Despite realizing this strange thing for a long time, however, experts have only discovered the mechanism of reflex activity in recent times.

Initial assumptions

The great Greek philosopher Aristotle in 350 BC asked a question in the first chapter of The Book of Problems: " Why is the heat of the sun sneezing? ". This is considered the first evidence for the discovery of the phenomenon of 'sneezing light' . At that time, Aristotle hypothesized that the sun's heat created moisture, sweat inside the nose and mouth, thus secrete more. To get rid of this dampness, the body forces us to sneeze.

Not until the 17th century, well-known philosopher and scientist Francis Bacon, also embarked on the search for the mysteries surrounding human sneezing reflexes . He proved that the theory Aristotle gave was incorrect, by looking at the sun with his eyes closed. As a result, no sneezing was done. Therefore, he thought that looking at the sun causes people to shed tears, then tears flow into the nose and cause sneezing.

However, scientists also disagreed with this view, simply because sneezing occurred too quickly after exposure to light. And tearing takes a certain amount of time to take place.

The mystery gradually came to light

In 1964, a new study yielded extremely positive results, by proving that the sneezing reflex is actually a genetic trait . If a parent experiences this condition, the probability of their children also having signs of light sneezing is 50%.

In 1978, Dr. Roberta Pagon and his colleagues took a further step in the search for the answer to this special phenomenon.

While attending a seminar on birth defects , the problem of light sneezing reflexes is in place. After a quick survey, 4 out of 10 doctors in the discussion said they and their families were more likely to be sneezed when exposed to sunlight. Not only that, repeated sneezing has many overlaps in each family member, but is different in other families. Describing this, Dr. Pagon said: "One person said most of their family sneezes 5 times continuously, with my family 3 times, and another person has only 1 time".

This is considered an important clue to the final conclusion. After the process of research together, scientists were able to determine the exact name of this thorny phenomenon: ACHOO Syndrome.

ACHOO Syndrome

So what happens in the body that led to this strange symptom? In 2010 a study conducted by Professor Nicholas Langer of the University of Zurich (Switzerland), attempted to decode AHCOO by examining the brain response of people sneezing by sunlight and those not suffer from that syndrome.

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Trigeminal nerve sends a signal to the brain when the nose is stimulated.

Thanks to an EEG, Dr. Langer came up with a surprising result: "Sneezing light reflection is completely unlike conventional reflexes, which occur only in the brain stem or spinal cord. It appears As for other cortical areas, 'he said . With what was observed from the EEG electrophoresis, he made two assumptions why sneezing due to sunlight.

First hypothesis: the visual system in the brains of people with AHCOO syndrome is much more sensitive than ordinary people. Too much light makes other parts of the brain panic, including somatosensory systems , known to control sneezing. In addition, his other hypothesis is a bit more complicated, but quite close to the concept of Aristotle and Bacon.

According to Dr. Langer, a light sneeze is also formed when our nose is stimulated by a certain cause.Cranial nerve V (tricuspid, trigeminal) is responsible for controlling the body when it is stimulated. When exposed to sunlight, the trigeminal nerve (located next to the optic nerve) sends image information from the retina to the brain.

Therefore, if the sun shines directly into our eyes, the retina suddenly shines a high amount of light, the optic nerve sends signals to the brain to order the pupil to contract. In theory, this signal can be perceived by the trigeminal nerve, the brain is mistaken for the irritated nose, and the result is one (or more) sneezes are formed. Up to now, the two views that Nicholas Langer offers are the most accepted scientific community.