Do you ever noticed people sneezing or sneezed when exposed to bright light like Sun? This is a special reflex that only 25% of people have this reflex. Those people are called Sun sneezers. The phenomenon is called Sun sneezing or Photic sneezing reflex.
The scientific reason behind it?
This is due to the confusion of nerve signals whose path ways are nearer to each other. Those nerves are Trigeminal nerve and Optic nerve. Both are called Carnial nerves which are 12 pairs of nerves arising directly from the brain. These nerves are responsible for sensing information from the sense organs. Whenever we stepout into bright light, the bright light entering the eyes sends a signal to brain via optic nerve which in turn sends signal to eyes to constrict the pupil. This a automatic reflex done to protect the eyes from light and is called pupillary light reflex. The sneeze reflex which works when there is a tickling in the nose, trigeminal nerve is in adjacent with the Optic nerve (responsible for pupil constriction). The trigeminal nerve interacts and also gets the signal from the optic nerve due to the nearness and the sneez reflex is activated. This is how some people sneeze when they are exposed to sunlight.
This is due to the confusion of nerve signals whose path ways are nearer to each other. Those nerves are Trigeminal nerve and Optic nerve. Both are called Carnial nerves which are 12 pairs of nerves arising directly from the brain. These nerves are responsible for sensing information from the sense organs. Whenever we stepout into bright light, the bright light entering the eyes sends a signal to brain via optic nerve which in turn sends signal to eyes to constrict the pupil. This a automatic reflex done to protect the eyes from light and is called pupillary light reflex. The sneeze reflex which works when there is a tickling in the nose, trigeminal nerve is in adjacent with the Optic nerve (responsible for pupil constriction). The trigeminal nerve interacts and also gets the signal from the optic nerve due to the nearness and the sneez reflex is activated. This is how some people sneeze when they are exposed to sunlight.
For most people the trigeminal nerve and optic nerve does not interact. Only for the Sun sneezers it is. The result? Exposure to bright light sends a signal to the brain to constrict the pupils, but the crossed nerve causes a sneeze as well.
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