The sneeze, or sternutation, is a rapid, involuntary reflex action designed to forcefully expel irritants from the nasal passages. This powerful biological mechanism serves as a protective function, clearing the airways of foreign particles like dust, pollen, and microbes. While the reflex is generally harmless, the sheer physical force and rapid pressure changes involved mean that in specific, often rare, circumstances, sneezing too hard can indeed cause physical injury.
The Physics of a Forceful Sneeze
The act of sneezing is preceded by a deep inhalation, which is immediately followed by a rapid, forceful contraction of multiple muscle groups. This process builds up immense, though temporary, pressure in the chest and respiratory system. The diaphragm and the intercostal muscles between the ribs contract suddenly, acting like a bellows to compress the air in the lungs.
Air is then explosively released through the nose and mouth, carrying expelled material at a high velocity. While early estimates suggested speeds over 100 mph, modern studies indicate the maximum velocity is closer to 10 miles per hour. Even at this lower speed, the sudden pressure surge against the body’s internal structures is significant, creating the potential for physical strain and injury.
Common Minor Injuries
The most frequent consequence of a forceful sneeze is a musculoskeletal strain, particularly involving the muscles supporting the rib cage. Intercostal muscle strain results from the sudden, violent contraction overstretching the muscles between the ribs. This causes localized sharp chest pain that worsens with movement or deep breathing, but it generally heals within a few weeks.
The forceful pressure generated can also lead to minor vascular damage in delicate areas, such as the eyes. A subconjunctival hemorrhage occurs when tiny capillaries rupture beneath the clear outer layer of the eye. This causes a bright red patch that looks alarming but is painless and resolves naturally as the body reabsorbs the blood.
A sudden, strong sneeze also creates an immediate spike in intra-abdominal pressure that can momentarily overwhelm the pelvic floor muscles. This commonly causes a brief, temporary episode of stress incontinence, particularly in women who have given birth or in older individuals.
Rare but Serious Complications
While most sneeze-related injuries are benign, the high internal pressure can lead to more serious, though uncommon, structural complications. A rib fracture is one possibility, especially in individuals with pre-existing conditions like osteoporosis or chronic coughing. The violent muscular spasm can exert enough force to break a rib, particularly where the bone is naturally more curved and vulnerable.
Damage to the spine is another rare issue, caused by the sudden, uncontrolled flexion and extension of the torso. A forceful sneeze can potentially cause a herniated or slipped disc, especially in the neck or lower back where a disc may already be compromised. The abrupt movement combined with the pressure can push the soft inner material of a vertebral disc out of its normal position, leading to pain and nerve impingement.
The tremendous pressure can also travel up the Eustachian tubes, which connect the back of the nose to the middle ear. In rare instances, this sudden influx of air pressure can rupture the eardrum, resulting in sharp pain and temporary hearing loss. Exceptional cases involve vascular events, such as the rupture of a pre-existing cerebral aneurysm, though these are linked to individuals with underlying vascular weaknesses.
Why You Should Never Suppress a Sneeze
The danger of a sneeze is significantly amplified not by letting it out, but by attempting to stop the reflex. When a person pinches their nose and closes their mouth to stifle a sneeze, the pressure is redirected back into the internal cavities of the head and chest. This rerouted pressure can be up to 24 times greater than the pressure released during an open sneeze, increasing the risk of localized damage.
The consequences of suppression can range from severe sinus pain to the rare but documented event of a pharyngeal rupture (a tear in the throat tissue). Redirecting the force inward can also push air into the middle ear through the Eustachian tube with enough power to cause barotrauma and burst the eardrum. To mitigate the risk of injury, allow the sneeze to exit naturally, perhaps turning into the crook of the elbow or slightly bending the knees to soften the impact on the back.