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Achoo! Understand the Science Behind Sneezing

What Causes Sneezing?

Sneezing is a mysterious bodily function. It’s not something you can control and it can sneak up on you at inopportune times with no warning.

The trigeminal nerve is the largest of the body’s 12 cranial nerves. With tiny sensors all over the face it sends information to the central nervous system from the forehead, eyes, nose, cheeks, jaw, skin and the mucosal lining inside the nose and mouth. When an area within the territory of trigeminal nerve is stimulated, the result can be a sneeze.

Common Sneeze Stimulants

Most sneezes are due to allergens like dust or dander, or sickness like the flu or a cold that irritate the mucosal lining of the nose. You may also sneeze when you are exposed to a chemical or environmental trigger like cigarette smoke, dry air or perfume. In these cases, the nasal passages have been stimulated and the body is ridding itself of an irritant.

However, the trigeminal nerve can be stimulated in other ways, too. According to a review of the sneeze reflex published in the journal Therapeutic Advances in Respiratory Disease, some people experience sneezing when they tweeze their eyebrows or receive injections around the eye. The article also reports that up to 35 percent of people sneeze when they are exposed to bright light like the sun, which scientists speculate could be a chain reaction of the optic nerve triggering the trigeminal nerve.

“Sneezing is actually a pretty interesting and complex reaction,” said Family Nurse Practitioner Vanessa Mizak, Samaritan Medical Group Pulmonology - Corvallis. “Once the brain receives the message that there is an intruder, a multi-part sneeze reflex is activated that coordinates several different systems and muscles in the body.”

Don’t Smother Your Sneeze

Whatever the cause of your sneeze, Mizak recommends letting it happen naturally. Holding in a sneeze can keep in bacteria that the body is trying to discharge and has been known to damage blood vessels, sinuses and eardrums.

“There is a lot of force behind a sneeze and your body is doing it for a reason,” Mizak said. “A clean tissue can help keep things tidy, but the crook of your arm is a good second choice to avoid spraying others.”

Practicing good sneeze etiquette can help cut down on the transmission of germs. The Centers for Disease Control and Prevention reports that sneeze droplets can travel six feet or more, and the germs that are transmitted can linger in the air and on surfaces that can infect others.

Masks & Sneeze Etiquette

Wearing masks in public has made the issue of sneeze etiquette a little more confusing. If you are around other people and feel the need to sneeze, try to go outside or at least step away, recommends Mizak. If that’s not possible, the next best choice is to leave your mask on and sneeze or cough into your elbow, just like you would if you weren’t wearing a mask. Replace your soiled mask with a fresh one as soon as possible since a damp mask may not be as effective at filtering out respiratory droplets from others.

“Wearing a mask stops larger droplets from getting into the air, but small droplets can still escape,” she says. “Sneezing into your elbow helps give a solid barrier to stop those tiny particles.”

She notes that infectious droplets can cling to your clothing and pass to others after you’ve sneezed, so continue to follow social distancing guidelines and don’t let others hug or touch you.

“Allergies are very common this time of year which can make wearing a mask annoying if your nose is running and you keep sneezing,” says Mizak. “Keep an extra mask in your pocket when you go out so you have a clean one if you need it, and talk to your doctor if allergies are starting to interfere with your quality of life.”