The sneeze, known medically as sternutation, is a forceful, involuntary reflex designed to clear irritants, such as dust or microbes, from the nasal passages. This protective mechanism begins when sensory nerves detect foreign particles, triggering a rapid, coordinated expulsion of air from the lungs. While many people instinctively try to stifle a sneeze, this common behavior forces the high-velocity air back into the body, creating potentially harmful internal pressure.
The Physics of a Sneeze
The sneeze begins with a deep inhalation, followed by the sudden, powerful contraction of the chest, abdominal, and pharyngeal muscles. This muscular effort creates a substantial volume of highly pressurized air within the respiratory system and nasal cavity. During a normal, unobstructed sneeze, this air is expelled at speeds up to approximately 16 meters per second (35 miles per hour).
The force generated causes a rapid spike in internal pressure, which is normally vented through the nose and mouth. When the nasal and oral passages are deliberately closed, the pressure has nowhere to escape. Research has shown that blocking the exit routes can increase the pressure within the upper respiratory tract by a factor of 5 to 24 times compared to an open sneeze.
Potential Injuries from Suppressing a Sneeze
Redirecting the high internal pressure from a suppressed sneeze can lead to barotrauma, which is physical damage caused by pressure differences. One of the most common issues is damage to the ear, since the Eustachian tube connects the back of the nose to the middle ear. The sudden rush of pressurized air up this tube can cause severe pain, drive infected mucus into the middle ear, or, in rare cases, rupture the tympanic membrane (eardrum).
The throat and neck are also vulnerable to damage from the redirected force. The pressurized air can be forced into soft tissues, leading to a pharyngeal rupture, a tear in the back of the throat. This injury can cause immediate pain, neck swelling, and difficulty swallowing or speaking. In other instances, the air may be pushed into the chest cavity, causing subcutaneous emphysema, where air becomes trapped under the skin, creating a crackling sensation.
Vascular structures are susceptible to the sudden increase in pressure. The brief but intense pressure spike can rupture small, superficial capillaries, particularly in the eyes, resulting in a subconjunctival hemorrhage—a patch of bright red blood on the white of the eye. While alarming, this is typically harmless and resolves on its own. However, the momentary pressure surge also carries a small risk of rupturing a pre-existing cerebral aneurysm, a weakened blood vessel in the brain.
In extremely rare cases, the immense pressure can cause more widespread mechanical injuries throughout the torso. The force has been known to cause muscular strain or, in rare instances, a fractured rib, particularly in individuals with underlying conditions. Although the likelihood of any single injury is low, it is advised to let the reflex occur naturally.
Recommended Alternatives to Suppression
Instead of forcibly clamping the nose and mouth shut, the best practice is to allow the sneeze to happen while minimizing the spread of respiratory droplets. The most hygienic method involves sneezing into a disposable paper tissue, which should be immediately discarded. Following this, washing hands thoroughly with soap and water is recommended. If a tissue is not immediately available, the next best alternative is to sneeze into the crook of the elbow or the upper sleeve. This technique directs the expelled air and droplets away from the hands, which are the primary vectors for spreading germs.