Sneezing after touching the nose is a common reaction. This reflex highlights the intricate connections within our sensory system, showing how even a gentle touch can initiate a forceful expulsion of air.
Understanding the Sneeze Reflex
The sneeze reflex is an involuntary bodily response designed to clear irritants from the nasal passages. This protective mechanism begins when sensory nerve endings in the nasal lining detect an irritant, such as dust or pollen. These nerve endings transmit a signal through a nervous system pathway to the brainstem’s sneeze center.
Once the sneeze center receives this signal, it orchestrates a rapid series of muscular contractions. This involves the chest and abdominal muscles, which compress the lungs and force air upward. The back of the tongue elevates, partially closing the mouth, which directs air forcefully out through the nose and mouth, expelling the irritant. The process happens within seconds, with air expulsion speeds reaching nearly 100 miles per hour.
The Nose’s Sensory Nerves
The face and nose are supplied with sensory nerves, primarily branches of the trigeminal nerve (cranial nerve V). This cranial nerve transmits sensations of touch, pressure, temperature, and pain from the head and face to the brain. The trigeminal nerve has three main divisions: the ophthalmic, maxillary, and mandibular nerves.
The ophthalmic and maxillary branches are particularly relevant to the nose and surrounding facial area. The ophthalmic nerve provides sensation to the forehead, eyelids, and the upper nose. The maxillary nerve covers the middle face, including the cheeks, lower eyelids, upper lip, and the inside of the nose and sinuses. These nerve endings are distributed, making the nasal region highly sensitive to stimuli.
How Touching Your Nose Triggers a Sneeze
Touching the nose, especially the sensitive lining inside, can directly stimulate trigeminal nerve endings. When activated by a mechanical stimulus like a touch or pinch, these nerve endings send signals to the brainstem. This signal travels to the sneeze-evoking region.
The close proximity and “crosstalk” between sensory pathways in the brainstem mean a touch stimulus, while not a typical irritant, can inadvertently activate the sneeze reflex pathway. Research suggests a neuropeptide called neuromedin B (NMB) is involved in signaling sneezing. NMB is released from sensory neurons to activate specific neurons in the sneeze-evoking region, which then drives the sneeze.
Is This a Common Phenomenon?
The phenomenon of sneezing when touching one’s nose is a recognized physiological response, although the exact frequency can vary among individuals. While it may seem unusual, it generally indicates a heightened sensitivity of the nasal passages and the trigeminal nerve network. This reaction is part of the body’s protective mechanisms, even when the stimulus is a benign touch rather than a harmful irritant.
Some sources suggest that factors such as bristly nasal hairs or a generally sensitive nasal lining can contribute to this specific reflex. It is considered a normal variation in how individuals respond to sensory input in the nasal area. In many cases, it is simply a demonstration of the intricate and sometimes overreactive nature of our sensory nervous system.