A sneeze (sternutation) is a forceful, involuntary expulsion of air from the lungs through the nose and mouth. This sudden burst of air is the body’s protective mechanism, designed to rapidly clear the nasal passages of irritants and foreign particles. Many people report a distinct feeling of satisfaction or relief immediately following a successful sneeze, prompting the question of why a basic reflex can feel so good.
The Mechanics of the Sneeze Reflex
The physical process begins when an irritant, such as dust, pollen, or a sudden change in temperature, stimulates sensory nerve endings in the nasal lining. This stimulation activates the trigeminal nerve, which transmits the signal to the “sneeze center” located in the brainstem. This brainstem region then coordinates the entire complex, involuntary reflex arc.
The body prepares for the expulsion by taking a deep breath and tensing the chest muscles. In a complex, rapid sequence, the eyes involuntarily close, the soft palate and uvula depress, and the tongue moves back. The final, explosive release involves the diaphragm and chest muscles contracting violently to generate the necessary force to clear the nasal cavity.
The Neurochemical Basis for Relief
The feeling of intense satisfaction is primarily a response to the relief of accumulated physical and nervous pressure. Before the sneeze is fully executed, a period of heightened internal tension builds up as the body anticipates the powerful action. The body’s nervous system perceives this mounting pressure from the irritated nasal passages and the contracting muscles.
The sudden, forceful release of this pressure registers as a fleeting sense of well-being. The intense physical effort and subsequent relaxation may stimulate the vagus nerve, which runs from the brainstem to the abdomen and influences the parasympathetic nervous system. This stimulation, coupled with the immediate cessation of discomfort, is thought to trigger a temporary surge of pleasure-related neurochemicals.
The involuntary contraction and immediate relaxation of the muscles provide a deep proprioceptive sensation that the brain interprets as satisfying. This resolution of intense excitation and the successful completion of a protective reflex is intrinsically rewarding. The momentary satisfaction is a powerful signal that the body has successfully cleared an obstruction.
Practical Considerations: Why You Shouldn’t Hold It In
Given the immense physical forces involved, it is inadvisable to suppress or stifle a sneeze once the reflex has begun. A sneeze is designed to expel air with significant velocity, and blocking this pathway forces the pressure to redirect internally. Studies have estimated that holding in a sneeze can increase the internal pressure within the respiratory system to a level 5 to 24 times greater than a natural sneeze.
This trapped force can lead to potential, though rare, injuries as the pressure seeks an alternate exit. Consequences include a ruptured eardrum, which occurs when the pressurized air travels up the Eustachian tubes into the middle ear. Redirected pressure can also cause a subconjunctival hemorrhage, which is a burst blood vessel in the eye, or, in extremely rare cases, damage to the throat or a brain aneurysm. Therefore, it is always best to simply let the reflex run its course.