Oscar, 7 years old: “Why does the sun make me sneeze? "

• Bright light can cause a sneeze in about a quarter of humans, according to our partner The Conversation.

• While you might think that sneezing is a phenomenon that occurs in the nose, most of it occurs in the brain.

• The analysis of this phenomenon was carried out by David Farmer, researcher in neuroscience at the University of Melbourne (Australia).

Very intelligent people have asked this question for thousands of years.

To tell you the truth, no one knows for sure why this is happening.

But that's probably because the signals sent from your eyes or nose are going to the same part of your brain.

The center of the sneeze

Your nose is used to smell and breathe.

But sometimes things that shouldn't be there get into our noses.

The list of things that should

be in your nose is very long, so I'm not going to cover everything.

But it includes things like viruses and bacteria, which are tiny germs that sometimes make us sick.

When you have something in your nose that shouldn't be there, it is best to call on the “sneeze center”.

This is the place in your brain that triggers sneezing.

It is found in the brainstem, which is located at the base of the brain.

It can do this because it contains instructions on how to activate your respiratory muscles in the correct order to produce a sneeze.

So while you might think that sneezing is a phenomenon that occurs in the nose, most of it occurs in the brain.

Activation of the sneeze center

It is commonly recommended that you put your hand in front of your mouth when sneezing or coughing.

You can also sneeze and / or cough in an elbow, the arm bent in front of you ... or sneeze in the 2 elbows, the two arms crossed in front of you, the hands on the side or behind © F. Lamiot / Wikimedia CC BY -SA 1.0

When you have things in your nose that shouldn't be there, they activate nerve cells inside your nose.

These nerve cells send a signal to the brain, which is conveniently located inside your head and not very far from your nose.

When the brain receives this signal, it transmits it to the sneeze center inside your brain to tell it "you really have to sneeze now."

The center of the sneeze then produces a sneeze that pushes unwanted objects out of your nose.

The sun

While the nose is very important, it's not the only part of your body that has nerve cells that communicate with the brain.

There are also the eyes.

Bright light in the eyes can cause a sneeze © Victoria Borodinova / CC0 Public Domain

Imagine you are looking at something very bright, which can be the sun but not necessarily.

Nerve cells in the eye send this information to the brain, which asks you to blink or squint in order to handle light.

However, for a reason that is still not well known, in about a quarter of people (including you!), Bright light can also cause a sneeze.

Why ?

Scientists disagree on this, but I'll tell you what I think is the most likely explanation.

Some of the nerve cells in your nose and eye communicate with the same area of ​​the brain: a place called the “trigeminal nucleus”.

This means that signals from the nose (those that usually cause a sneeze) and signals from the eye (those that usually cause squinting or blinking) arrive in the same part of the brain.

Our “BRAIN” file

If the number of signals coming from the eye is very high (as can be the case if you are looking at the sun), they can end up activating the sneeze center as

the parts of the brain that cause the eyes to blink. .

It makes you sneeze, even without putting anything in your nose!

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This review was written by David Farmer, neuroscience researcher at the University of Melbourne (Australia).

The original article was published on The Conversation website.

Declaration of interests

David Farmer does not work, advise, own shares, receive funds from any organization that could benefit from this article, and has not declared any affiliation other than his research organization.

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