A sneeze (sternutation) is a rapid, involuntary protective reflex that forcefully expels irritants from the nasal passages. People often try to induce a sneeze when irritation does not resolve naturally. Investigating the safety of initiating this reflex reveals a difference between the consequences of forcing and blocking the expulsion.
The Mechanics of a Natural Sneeze
The sneeze reflex begins when receptors in the mucous membranes of the nasal cavity detect an irritant, such as dust, pollen, or microbes. This sensation activates the trigeminal nerve, which transmits the signal to the brainstem where the sneeze center is located. The brain then coordinates a sequence of involuntary muscular actions designed to clear the airway.
This complex reflex involves a deep inhalation, followed by a sudden, forceful expiration against a momentarily closed glottis. Muscles in the diaphragm, abdomen, pharynx, and chest contract to generate a significant burst of air pressure. This pressure is then released suddenly through the nose and mouth, ejecting the irritant at a high velocity.
Potential Risks of Manually Triggering a Sneeze
Trying to make yourself sneeze is generally considered low-risk. Methods like looking toward a bright light or tickling the inside of the nose artificially stimulate the same nerve pathways. The photic sneeze reflex is a hereditary trait where bright light stimulates the trigeminal nerve alongside the optic nerve.
Any risk associated with forcing a sneeze comes from the method of induction rather than the expulsion itself. Aggressive mechanical stimulation, such as inserting a tissue too deeply, can cause minor trauma to the delicate nasal lining. This lining contains sensitive tissue and small blood vessels that can be easily irritated or damaged by abrasive contact.
While the resulting sneeze is similar to a natural one, the forceful muscle contractions can cause minor, temporary strain. Artificially inducing the reflex may lead to a momentary spike in pressure, occasionally resulting in brief lightheadedness or a mild headache. Compared to stifling a sneeze, intentionally triggering one poses minimal threat.
Why Suppressing a Sneeze is More Dangerous
Suppressing a sneeze by pinching the nose and closing the mouth is significantly more dangerous than forcing one out. A sneeze generates pressure that needs an outlet; when blocked, the pressure is redirected internally. The air pressure behind a stifled sneeze can be up to 5 to 20 times greater than a normal sneeze.
This immense, contained force can be transmitted into the sinuses and up the eustachian tubes into the middle ear. Redirected pressure may damage the eardrums, potentially leading to a ruptured eardrum or ear infection if infected mucus is forced inward.
In rare cases, high internal pressure has resulted in more severe injuries, including the rupture of small blood vessels in the eyes or nose. Extremely rare instances have also reported damage to the throat, a collapsed lung, or the rupture of a brain aneurysm in individuals with pre-existing conditions. Allowing the sneeze to complete its natural function is the safest course of action.