Why do we sneeze?

Sneezing is a protective reflex. Nerve endings in the nasal lining detect an irritant, whether dust, pollen, pepper, or inflammation from infection, and send a signal to the brainstem, which coordinates a rapid sequence: a deep breath, closure of the throat, and a forceful contraction of chest and abdominal muscles that expels air through the nose and mouth. High-speed imaging has shown the resulting spray travels much further than was long assumed, producing a turbulent cloud of droplets that can carry across a room, which is why sneeze etiquette became a public health topic rather than merely a courtesy one.

Some triggers are peculiar. Roughly a fifth to a quarter of people experience the photic sneeze reflex, sneezing when moving suddenly into bright light, an inherited trait thought to result from crossed signaling between the optic and trigeminal nerves. Some people sneeze after a large meal, and some after plucking eyebrows, both attributed to related nerve proximity. Sneezing generally does not occur during sleep because the relevant nerves are suppressed.

One practical warning: suppressing a sneeze by pinching the nose and closing the mouth redirects considerable pressure inward, and documented case reports include ruptured throat tissue, damaged eardrums, and in rare instances air forced into tissue around the lungs. The safe approach is to sneeze into a tissue or your elbow rather than to hold it in. Two related notes: sneezing more than a few times in a row is common and unremarkable, and persistent unexplained sneezing alongside congestion often points to allergic rhinitis, which is worth identifying since it responds well to treatment. The heart does not stop when you sneeze, though the pressure changes can briefly alter its rhythm, which is where that belief comes from.