Why Do We Sneeze? An Evolutionary Biologist Explains

Key Points:

• Sneezing is a highly coordinated, ancient biological reflex designed primarily to clear irritants from the nasal passages, protecting respiratory tissues from dust, pathogens, and allergens.
• The reflex involves sensory receptors in the nose detecting irritation, signaling the brainstem's "sneeze center," which triggers a rapid, forceful expulsion of air at speeds up to 100 km/h to eject mucus and particles.
• Eye closure during sneezing is not to prevent eyes from popping out but is part of the reflex involving facial muscles, likely serving to protect the eyes from expelled debris.
• About 25% of people experience the photic sneeze reflex, where bright light triggers sneezing due to heightened brain sensitivity linking visual and sensory processing areas, rather than a simple brainstem reflex.
• Many mammals, birds, and some reptiles sneeze to clear respiratory passages, but not all animals do, as sneezing requires specific respiratory anatomy and nervous system coordination tied to air-breathing life on land.