What happens in my body when I sneeze?

September 27, 2025 •

4 min read

The average sneeze can travel at a speed of up to 100 miles per hour, expelling a cloud of tiny droplets into the air. This powerful, automatic response is triggered by an irritation in your nasal passages, leading to a complex series of events. Discover exactly what happens in your body when you sneeze.

Quick Summary

A sneeze is a rapid, involuntary expulsion of air from the lungs through the nose and mouth, triggered by a nerve impulse from the trigeminal nerve. It involves a cascade of muscular and physiological events orchestrated by the brain to clear irritants from the nasal cavity.

Key Points

Reflex Initiation: A sneeze begins when irritants like dust or pollen trigger nerves in the nose, sending a signal to the brainstem's sneeze center.
Pressure Buildup: The body takes a deep, involuntary breath, and muscles in the chest and diaphragm contract to build up immense air pressure in the lungs.
Eye Closure: The eyes reflexively close tightly, a protective measure linked by nerves to prevent irritants from the sneeze from entering.
Forceful Expulsion: Air is expelled at high speed from both the nose and mouth, driven by powerful muscle contractions to clear the nasal passages.
Heartbeat Myth: It is a myth that your heart stops when you sneeze; the intense pressure can briefly affect heart rhythm, but it continues to beat.
Suppression Risks: Holding in a sneeze is not recommended, as the redirected pressure can potentially cause minor injuries to the ears, nose, or throat.

The Body's Protective Force: An Overview of the Sneeze Reflex

Sneezing, or sternutation, is far more than just a simple "achoo." It is a sophisticated protective mechanism designed to clear your nasal passages of foreign particles. This complex reflex arc involves multiple organ systems working in a coordinated, lightning-fast sequence. The journey of a sneeze begins with a tiny irritant and ends with a powerful, propulsive expulsion.

The Trigger: Identifying the Irritant

It all starts with a trigger. An irritant, such as dust, pollen, or a sudden change in temperature, enters the nasal cavity. The sensitive nerve endings lining the nose detect this foreign invader, sending a signal to the brainstem. The brainstem then alerts the sneeze center, a specialized region in the medulla, which orchestrates the entire event. This initial signal is transmitted via the trigeminal nerve, one of the most important cranial nerves.

The Preparatory Phase: Getting Ready to Explode

Once the sneeze center is activated, the body begins a rapid series of preparations. This is the moment when you feel that characteristic tickle in your nose and the irresistible urge to sneeze. Your body tenses, and you take a deep, involuntary breath. This deep breath is crucial; it builds up the air pressure in your lungs, providing the explosive force needed for the final expulsion.

The Eyes Close: A reflex action causes your eyes to shut tightly. While many people believe this is to prevent their eyeballs from popping out (a myth), the real reason is a bit more complex. The nerves that control the sneeze are closely linked to those that control eye movement, causing a simultaneous closing. It is a protective measure to prevent irritants from the sneeze from entering the eyes.

The Muscle Contractions: As you inhale, your chest muscles, diaphragm, and even your throat muscles contract. This action further increases the pressure in your respiratory system, building up the necessary power for the upcoming sneeze. The soft palate and the back of your tongue also rise, preparing to route the air.

The Expulsion: The Powerful Finale

The moment of expulsion is a rapid and forceful event. The accumulated air pressure is released in a powerful burst. Your diaphragm and chest muscles contract violently, forcing air out of your lungs. Simultaneously, your soft palate and uvula drop, causing the air to be expelled not only through your mouth but primarily through your nose. The characteristic sound is produced by the air being forced past these vibrating structures.

What About When You Hold a Sneeze In?

Some people try to suppress a sneeze, but this is generally not recommended. While not common, holding in a sneeze can redirect the immense pressure built up in your chest to other parts of your body. This can potentially lead to issues such as ruptured eardrums, damage to blood vessels in the nose or eyes, or, in very rare cases, even a ruptured throat or rib fracture. It's best to simply let the sneeze run its course.

Comparison: Sneeze vs. Cough

While both sneezes and coughs are reflex actions to clear the respiratory tract, they serve slightly different purposes and operate from different locations.


Feature	Sneeze	Cough
Trigger	Irritation in the nasal passages	Irritation in the throat, larynx, or lower respiratory tract
Primary Purpose	To clear irritants from the nasal cavity	To clear irritants and mucus from the throat and airways
Force Direction	Forceful expulsion primarily through the nose	Forceful expulsion through the mouth
Nerve Pathway	Trigeminal nerve	Vagus nerve
Involuntary Nature	Highly involuntary and difficult to suppress	Can sometimes be controlled or suppressed more easily

Fun Facts and Further Insights

Sleep Inhibition: It's impossible to sneeze while sleeping because the nerves involved in the reflex are also resting. During REM sleep, the neurotransmitters that control muscle reflexes are suppressed.
The Photic Sneeze: Approximately one-third of the population experiences the "photic sneeze reflex," which is triggered by bright sunlight. It is thought to be an error in the neural wiring that links the optic nerve with the trigeminal nerve.
Myth vs. Reality: The old myth that your heart stops when you sneeze is false. While the intense pressure can momentarily change blood flow and heart rhythm, it does not stop beating. The brief pause you might feel is simply a change in pressure.

For more information on respiratory health and bodily functions, you can refer to authoritative sources like the Mayo Clinic.

Conclusion

From the moment an invisible particle irritates a single nerve ending to the powerful expulsion of air, the sneeze is a marvel of human physiology. It's a rapid, well-orchestrated defensive maneuver that protects our bodies from potential harm. The next time you feel a sneeze coming on, you'll have a new appreciation for the complex series of events that are about to unfold within you.

Frequently Asked Questions

Your eyes close involuntarily during a sneeze due to a reflex action. The nerves that trigger the sneeze are connected to the nerves that control your eyelids, causing them to shut as a protective measure to keep irritants from the expelled air out of your eyes.

A sneeze can travel surprisingly fast, with estimates suggesting speeds of up to 100 miles per hour. This rapid velocity helps effectively expel irritants from the nasal cavity.

No, it is a persistent myth. Your heart does not stop when you sneeze. The change in chest pressure can cause a momentary change in your heart's rhythm, but it doesn't stop beating.

You cannot sneeze while sleeping because the nerves that initiate the reflex are also in a state of rest. During REM sleep, the neurotransmitters that trigger muscle contractions are suppressed, making a sneeze impossible.

The primary purpose of a sneeze is to clear your nasal passages of foreign particles, such as dust, pollen, or other irritants. It is a protective, involuntary reflex that keeps your respiratory system healthy.

Holding in a sneeze is not advisable because it can cause a buildup of immense pressure. This pressure could potentially cause minor injuries, such as a ruptured eardrum, a ruptured blood vessel in your nose, or, in very rare cases, more serious damage.

While frequent sneezing can be a symptom of a common cold or allergies, a single sneeze doesn't necessarily indicate sickness. It is most often just the body's natural response to an irritant in the nasal cavity.