Answer: If you sneeze when looking at a light, you are not alone! As many as one out of every three people seem to have this interesting phenomenon, called photic sneeze, in which bright light triggers a sneeze. Sir Francis Bacon even wrote about it, almost 400 years ago, "Looking against the Sunne, doth induce Sneezing." (Sylva Sylvarum)
We generally sneeze to get rid of something that is irritating the inside of our nose, such as dust, pollen, or viruses. The body uses lots of nerves and muscles to coordinate this protective reflex. Although no one knows exactly why photic sneezes happen, there are some theories. A popular one is that a sudden flash of bright light causes the nerve signal leaving the eye (along the optic nerve) to trigger a nearby nerve (trigeminal) that goes to the nose, thereby causing a sneeze. Another theory suggests that bright light causes the eye to make more tears, which drip into the nose and trigger a sneeze.
Photic sneezing does tend to run in families and scientists may find a photic sneezing gene one day. Perhaps some researchers even are looking for a way to stop photic sneezes from happening. Although you may find it helpful to glance at a bright light when you feel like you have to sneeze but can't, did you know that this reflex sometimes can be dangerous? For example, some people sneeze quite forcefully, which might cause problems if it happens when they are driving a car and exit a dark tunnel into bright sunlight, or are flying a fighter jet and have to turn suddenly into the sun. Sunglasses may help to prevent photic sneezes for some people.
Whatever the cause, remember that sneezing can spread germs, so cover your mouth and nose (with a disposable tissue or your upper arm) when you sneeze!
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