Sneezing

When we were college sophomores, my roommate, Susan, and I were housed in a room that was next to a sleeping porch. The porch was at the corner of the dormitory building. (This was 1959. The sleeping porches have since been removed, more’s the pity.) On warm nights, we’d sleep out there. In the mornings, as soon as the sun came into the porch, Susan would start sneezing. I thought it was simply an odd quirk.

Many years, later, I learned that her sunlight-induced sneezing is a genetic trait, one shared by 18 to 35 percent of the population. It even has a name: “photic sneeze reflex;” or, even better, “autosomal dominant compulsive helio-opthalmic outbursts of sneezing syndrome,” aka ACHOO. The number of sneezes, usually two or three, is constant. Even though sunlight-induced sneezing is rather common, scientists don’t know its exact mechanism.

Sneezing is an important part of your immune system. The sneeze reflex clears your nose of bacteria and viruses. Here’s how it works: a stimulant triggers the “sneeze center” located in your lower brain stem. The sneeze center sends signals to muscles, causing them to tightly close your throat, eyes, and mouth. Next your chest muscles vigorously contract, after which they quickly relax. As a result, air is forced out of your mouth and nose: you’ve sneezed.

Here are some sneezing factoids:

• Besides sunlight, eyebrow plucking, exercise, and having sex triggers sneezes in some people.
• Sneezes travel at about 100 miles an hour.
• A single sneeze can send 100,000 germs into the air.
• You don’t sneeze in your sleep (your sneeze center is also asleep).
• Iguanas sneeze more than any other animal. (Who counts such things?)

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