The common belief that the heart stops beating, or that a person “dies for a second” during a sneeze, is a persistent piece of folklore that has been passed down through generations. This myth stems from the powerful physical sensation that accompanies the body’s sudden, involuntary expulsion of air. The scientific truth is far less dramatic: the heart does not stop, nor does a person die, but the cardiovascular system does react to the profound changes in pressure within the body.
Debunking the Heart Stopping Claim
The heart continues to beat throughout a sneeze because the electrical signals from the sinoatrial (SA) node, the heart’s natural pacemaker, are not affected by the reflex. Sneezing does not interrupt the complex electrical pathway that coordinates the heart’s rhythm. The sensation of a skipped or stopped beat is actually a reaction to the rapid fluctuation of pressure within the chest cavity, known as intrathoracic pressure.
Before the explosive exhalation, a deep breath temporarily increases pressure in the chest, slowing the flow of blood returning to the heart. The heart compensates for this momentary change by altering its rhythm, often causing a slight delay in the next beat. This brief dip is further influenced by the vagus nerve, which is stimulated by the increased pressure and acts to reduce heart rate. The heart quickly returns to its normal pace after this brief pause.
The Physical Process of a Sneeze
A sneeze (sternutation) is a protective, involuntary reflex designed to forcefully clear the nasal passages of irritants. The process begins when sensory receptors in the nasal lining detect an irritant, such as dust or pollen. This detection triggers an electrical signal that travels along the trigeminal nerve to the medulla in the brainstem.
The brainstem coordinates a complex motor sequence involving muscles throughout the body. This sequence involves a deep inhalation, followed by the closure of the vocal cords and the back of the throat. Abdominal, chest, and diaphragm muscles contract forcefully against the closed airways. This coordinated contraction rapidly builds up pressure in the lungs and chest cavity, preparing for the expulsion phase.
The final stage is the explosive release, where the vocal cords suddenly open, allowing pressurized air to be expelled at speeds up to 100 miles per hour. This burst of air dislodges and ejects the irritating substance. The reflex is a synchronized event that clears the airways of contaminants.
Why Breathing Stops Temporarily
While the heart does not stop during a sneeze, breathing ceases temporarily, which is likely the origin of the misconception. This temporary cessation of respiration is an integral part of the sneeze reflex sequence. The process begins with a deep inhalation, filling the lungs with the air volume needed to generate force.
Once the lungs are full, the body halts the respiratory cycle by closing the glottis and the soft palate. This closure seals the airway, allowing chest and abdominal muscles to squeeze the lungs and build the high air pressure required for exhalation. The pause in breathing is a purposeful action that maximizes the force and effectiveness of the expulsion.
The eyes also close involuntarily as part of the neurological reflex. This protective measure prevents irritants and microorganisms expelled at high velocity from entering the eyes.