Stuff You Should Know

How Sneezing Works

March 20, 2026

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  • Sneezing is an ancient, involuntary reflex coordinated by a dedicated 'sneeze center' located in the lateral medulla of the brain, which acts as a fast bouncer to expel irritants from the nasal passages. 
  • The sneeze process involves two phases: the afferent phase (nerves sending irritation signals) and the efferent phase (the brain commanding the expulsion), which together occur in less than a second and involve numerous muscle groups, potentially expelling air at speeds up to 100 miles per hour. 
  • Various conditions, including allergies (rhinitis), exposure to irritants, hormonal changes, and even light exposure (photic sneezing), can trigger the sneeze reflex, which is genetically linked in some cases. 

Segments

Introduction to Sneezing Reflex
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(00:00:40)
  • Key Takeaway: Sneezing is an ancient, efficient, involuntary reflex designed to rapidly expel foreign matter from the nasal passages.
  • Summary: Sneezing is an ancient reflex common to most mammals, serving as a rapid expulsion mechanism for irritants. The nasal passages are narrow to create turbulence, forcing inhaled air against the nasal mucosa where cilia attempt to move particles toward the throat for swallowing. If particles adhere too strongly, specialized mast cells release histamines, triggering the full sneeze response.
Sternutation and Sneeze Center
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(00:03:07)
  • Key Takeaway: The scientific term for sneezing is ‘sternutation,’ and the reflex is coordinated by a specific ‘sneeze center’ in the lateral medulla of the brain.
  • Summary: The clinical term for sneezing is sternutation, a word dating back to 1576. The sneeze is initiated when irritation reaches a threshold, sending signals via nerves like the olfactory and trigeminal nerves to the sneeze center in the lateral medulla. This center then sends signals back to facial and body muscles to execute the forceful expulsion.
Reverse Sneeze in Dogs
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(00:05:21)
  • Key Takeaway: Dogs experience a ‘reverse sneeze,’ which is distinct from a true sneeze and often related to brachiocephalic anatomy.
  • Summary: Iguanas are noted for sneezing frequently as part of their digestion, but dogs often exhibit a reverse sneeze, which can sound alarming. This reverse action is not a true sneeze (expelling matter from the nose) but is often related to nasal passage issues in brachiocephalic breeds. Owners can sometimes help by lightly plugging the dog’s nostrils or stroking its throat.
Sneeze Mechanics and Force
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(00:10:57)
  • Key Takeaway: A sneeze is a violent action involving deep inhalation followed by forceful expulsion, with air velocity potentially reaching 100 miles per hour.
  • Summary: The sneeze involves a deep inhalation followed by the vocal cords clamping shut, building significant pressure in the thorax. The subsequent release forces air out through the mouth and nose at high speeds, sometimes causing physical strain or injury if the body is hunched over. Contrary to myth, it is impossible to pop one’s eyes out by keeping them open during a sneeze.
Causes of Rhinitis and Sneezing
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(00:21:40)
  • Key Takeaway: Sneezing is commonly caused by rhinitis (inflammation of the mucous membrane), but specific types include occupational, hormonal, and drug-induced triggers.
  • Summary: The most common cause of sneezing is rhinitis, often due to allergies or colds, though clinical terms like rhinorrhea describe a runny nose. Other triggers include occupational exposure (like cleaning supplies or flour), hormonal fluctuations (high estrogen), and certain medications such as NSAIDs and beta blockers. Geriatic rhinitis occurs when submucosal glands atrophy in older age, causing irritation.
Photic Sneezing Reflex
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(00:25:27)
  • Key Takeaway: Photic sneezing, or ACHOO syndrome, affects 23-25% of people and is an inherited trait where bright light triggers a sneeze via nerve crossover.
  • Summary: Photic sneezing is an autosomal dominant inherited trait where exposure to intense light, usually sunlight, causes sneezing, often in patterns of three for some individuals. This is hypothesized to be a crossover between the pupillary light reflex arc and the sneeze reflex arc. Looking toward a bright light can sometimes trigger the efferent (expulsion) phase if the afferent phase has already begun.
Arousal and Psychogenic Sneezing
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(00:33:54)
  • Key Takeaway: A small number of people experience sneezing triggered by sexual arousal or orgasm, possibly due to shared erectile tissue in the nose.
  • Summary: Some individuals sneeze when sexually aroused or after orgasm, a phenomenon anecdotally linked to the presence of erectile tissue in the nose, which swells with blood flow. Intractable or psychogenic sneezing, which can involve days of continuous sneezing, is almost exclusive to adolescent girls, exemplified by the record case of 977 days of sneezing.
Sneeze Contagion and Droplet Spread
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(00:40:48)
  • Key Takeaway: Sneeze droplets can travel up to 27 feet and remain suspended in the air for minutes, but outdoor air dissipation significantly reduces contagion risk compared to indoors.
  • Summary: High-speed video analysis shows sneeze droplets travel far, breaking from large clumps into fine, aerosolized particles that can hang in the air. While contagious germs might remain suspended for weeks indoors without airflow, outdoor factors cause rapid dissipation, making direct, close-range exposure the primary risk factor for transmission outside.
Cultural Responses to Sneezing
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(00:47:26)
  • Key Takeaway: Cultural responses to sneezing range from wishing good health (like ‘God bless you’) to interpreting it as an omen about being talked about.
  • Summary: In the West, saying ‘God bless you’ originated during the Black Plague as a prayer against death, contrasting with earlier Christian teachings to ignore sneezes. In China and Japan, sneezing is interpreted as a sign that someone is speaking about you; one sneeze is positive, two means gossip, and three traditionally meant death. Responding to a sneeze is often considered a ‘microaffection’—a brief, kind connection with a stranger.