Why do I sneeze when I walk into bright sunlight

Q. The photic sneeze

A. Yes, as named by Henry Everett, a physician at the Johns Hopkins University medical school, in 1964.

Q. Are there any theories as to why it happens

A. Oh yes, several.

Q. Like what..

A. That the sneeze is produced by the over stimulation of the optic nerve by the sudden exposure to increased light levels.

Alternatively some scientists suggest that the photic sneeze is an involuntary reflex, like breathing.

Q. Why do people makes photic sneezes

A. Either way the end result is though to be linked to the protective reflexes of the eyes, which are linked to the nose. When we sneeze we close our eyes for a split second and it may be that our body is trying to protect them from the sudden increase in light levels.

Q. What normally causes a sneeze

A. Normally, a sneeze is triggered when something stimulates your nose, sending a message to your brain via the trigeminal nerve. Then your body draws in air, shuts off the wind pipe and expels the air from your lungs which bursts out as a sneeze., blowing with it whatever irritated your nose in the first place.

Q. So, how does light have the same effect

A. According to Dr. Everett's original theory photic sneezers may have optic and trigeminal nerves that pass particularly close to each other where they enter the brain. When a bright light sends a strong signal along the optic nerve, that same signal may also stimulate the nearby trigeminal nerve.

Q. Does everyone do it

A. No, between 20 and 35% of us are prone to this phenomenon.

Q. Is it just sunlight that has this effect

A. No, some eye specialists have noted that some patients sneeze when they examine their eyes with bright lights.

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by Lisa Cardy