A sneeze is a common, involuntary reflex involving the sudden, forceful expulsion of air from the lungs through the nose and mouth. This rapid burst of air, also known as sternutation, protects the respiratory system.
The Body’s Coordinated Sneeze Reflex
A sneeze often begins with the irritation of the mucous membranes lining the nose. Common triggers include airborne particles like dust, pollen, and mold, as well as strong odors, cold air, or even sudden exposure to bright light, the photic sneeze reflex. Viruses and bacteria can also stimulate this reflex, initiating the reflex.
Once irritants stimulate sensory nerve endings in the nasal passages, signals travel along the trigeminal nerve, the fifth cranial nerve, to the brainstem. This nerve transmits sensations from the face and nasal cavity, initiating the reflex. The signals arrive at a specific area in the medulla oblongata, referred to as the sneeze center, which then coordinates the sequence of events.
The brain sends signals to various muscles throughout the body. The eyes involuntarily close, and muscles in the throat, chest, and abdomen contract. The diaphragm also contracts, causing a deep inhalation followed by a powerful exhalation. The vocal cords briefly close before opening, allowing a high-velocity stream of air to burst forth through both the nose and mouth, often reaching speeds up to 100 miles per hour.
The Essential Role of Sneezing
Sneezing serves as a protective mechanism for the body, designed to clear the nasal passages. This reflex expels foreign particles, irritants, and excess mucus that have entered the nasal cavity. By forcefully ejecting these substances, sneezing helps prevent them from traveling further into the respiratory system.
The expulsion of irritants like dust, allergens, or pathogens helps safeguard the sensitive lining of the nose and throat. Some research also suggests that sneezing may help reset the cilia, restoring their ability to move mucus and trapped particles. This cleansing action is a rapid and effective defense against potential invaders or blockages in the respiratory tract.
What Happens When a Sneeze is Held Back?
Suppressing a sneeze involves blocking the natural, forceful expulsion of air, leading to a significant buildup of internal pressure. This pressure can be anywhere from 5 to 24 times greater than during an uninhibited sneeze, as the air is redirected internally instead of being released outward. While the body is resilient, this sudden pressure increase can, in rare instances, lead to various consequences.
One potential, though uncommon, outcome is a ruptured eardrum, as the pressurized air can be forced into the middle ear through the Eustachian tubes. Small blood vessels in the eyes or nose might also rupture, causing visible red spots or minor nosebleeds. While less frequent, forcefully holding back a sneeze has been linked to throat damage, including tears or ruptures in the pharynx.
In rare cases, the immense pressure can cause serious issues, such as injury to the diaphragm or pneumomediastinum, where air becomes trapped in the chest cavity. For individuals with pre-existing conditions like a brain aneurysm, the sudden pressure surge carries a low risk of rupture. Given these potential risks, allowing a sneeze to occur naturally is advisable.