Sunny Sneezes

Question

A woman covers her mouth as she sneezes.

Credit: Y.Gurevich/iStock/Getty Images Plus

The afternoon bell rings. Thirty students pile out of the classroom, hurry down the hall, and step outside into dazzling sunshine. Some smile up at the brilliant blue sky, while others squint and reach for their sunglasses, but a few have another reaction—a…a…achoo!

Does that scenario sound familiar? It's a real thing—some people sneeze whenever they are suddenly exposed to bright light. Scientists call this condition the photic sneeze reflex (PSR). (Photic means "having to do with light.")

An Age-Old Mystery

People have been trying to sniff out the truth about "sun sneezing" for a very long time. More than 2,000 years ago, scholars in ancient Greece proposed an explanation, and people have come up with other theories since then. Even today, however, scientists aren't entirely sure what causes PSR.

The Reason for the Sneezin'

Most experts believe photic sneezes result from some mixed-up signals to the brain. Two nerves with different jobs, the trigeminal and optic nerves, happen to be neighbors. The trigeminal nerve sends messages from the nose to the brain. Let's say there's dust irritating your nose. The trigeminal nerve signals your brain—and you sneeze to expel the troublesome stuff. Nearby is the optic nerve, which sends messages from the eyes to the brain. Bright light stimulates the optic nerve and usually makes people's pupils get smaller. But, for photic sneezers, bright light may have another effect. Scientists theorize that the electrical signal traveling through the optic nerve gets picked up by the trigeminal nerve as well. The body reacts as if something is irritating the nose, triggering a sneeze.

Who Has ACHOO?

While there hasn't been a lot of reliable research on the subject, it's estimated that between 10 and 35 percent of the population has PSR. This trait is passed down genetically, and it's dominant, meaning people can inherit it if one or both of their parents has it. PSR also has an alternative scientific name—autosomal-dominant compelling helio-ophthalmic outburst syndrome. That might sound like a terribly technical tongue twister, but its acronym is easy to remember and pronounce—ACHOO!

Answer 1

Photic sneezes, also known as ACHOO, can be quite common, affecting up to 35% of the population. This condition is passed down genetically and occurs when the optic nerve stimulates the trigeminal nerve, causing the body to react as if there is something irritating the nose and triggering a sneeze. Although scientists are still unsure of the exact cause, they believe it is due to mixed-up signals in the brain. So next time you see someone sneezing in the sunshine, you'll know they're experiencing the photic sneeze reflex!

Answer 2

Based on the article, which of these is true?

A.The trigeminal and optic nerves have very similar purposes.
B.People have been trying to figure out the truth about sunny sneezes for a long time.
C.The trigeminal and optic nerves are located far apart in the body.
D.Scientists agree that more than half of the population experiences sunny sneezes.

Answer 3

B. People have been trying to figure out the truth about sunny sneezes for a long time.

Answer 4

Which is most important to include in a summary of this article?

A.Scholars in ancient Greece proposed an explanation for "sun sneezing" 2,000 years ago.
B.The trigeminal and optic nerves send electrical signals to the brain.
C.Some people sneeze in bright light when two nerves get their signals crossed.
D.Experts think that the photic sneeze reflex (PSR) affects 10 to 35 percent of people.

Answer 5

C. Some people sneeze in bright light when two nerves get their signals crossed.

Answer 6

Which passage from the article best supports the idea that sunny sneezes are inherited?

A.Scientists theorize that the electrical signal traveling through the optic nerve gets picked up by the trigeminal nerve as well.
B.This trait is passed down genetically, and it's dominant, meaning people can inherit it if one or both of their parents has it.
C.The trigeminal nerve signals your brain—and you sneeze to expel the troublesome stuff.
D.Even today, however, scientists aren't entirely sure what causes PSR.

Answer 7

B. This trait is passed down genetically, and it's dominant, meaning people can inherit it if one or both of their parents has it.

Answer 8

Read this sentence. If you know that the word concept means an idea, can you figure out what the word misconception means? Write the definition of the word in the text box below. Click SUBMIT when you are done.

There is a popular misconception that exercise is bad for your heart.

Answer 9

Misconception: a mistaken or incorrect belief or understanding.