Why We Sneeze: The Mechanics of a Sneeze and Breathing Myths

A sneeze (sternutation) is a powerful, reflexive expulsion of air from the lungs through the nose and mouth, triggered by nasal mucosal irritation.

Physiological Sequence

1. Trigger: Irritants (dust, allergens, viruses, bright light—photic sneeze reflex) stimulate trigeminal nerve endings in nasal mucosa.
2. Afferent Pathway: Trigeminal → sneeze center (lateral medulla near respiratory centers).
3. Inspiratory Phase: Deep inhalation (2–2.5 L) via diaphragm and external intercostals; glottis closed; pressure builds.
4. Compression Phase: Vocal cords close; abdominal and internal intercostal muscles contract forcefully → intrathoracic pressure ↑ to 100–200 mmHg.
5. Expulsive Phase: Vocal cords open suddenly; high-velocity jet (up to 100 mph / 45 m/s) ejects air, mucus, and irritants through nose/mouth.
6. Recovery: Brief apnea, then normal breathing resumes.

Common Myths Debunked

• "Your heart stops when you sneeze." False. Intrathoracic pressure changes transiently affect venous return and heart rate (reflex bradycardia then tachycardia), but cardiac electrical activity continues uninterrupted.
• "You can't sneeze with your eyes open." False. Eye closure is a reflex (facial nerve), but voluntary override is possible.
• "Sneezing expels the soul / evil spirits." Cultural folklore; no biological basis.

Hygiene and Safety

• Cover with tissue or elbow (not hands) to limit droplet spread (up to 8 meters).
• Wash hands immediately.
• Do not suppress a sneeze by pinching nose/closing mouth—can cause tympanic membrane rupture, pneumomediastinum, or vascular injury.

Sneezing is a protective reflex clearing the upper airway. It does not stop breathing; it requires a deep breath first.