Sneezing immediately after starting to brush your teeth is a surprisingly common phenomenon. While this reaction may seem like a random event, it has a clear neurological explanation. It is a harmless instance of sensory nerves getting momentarily confused, sending signals that mistakenly initiate the sneeze reflex.
The Trigeminal Nerve Connection
The scientific reason for this oral-nasal connection lies with the Trigeminal nerve, known as Cranial Nerve V, which is the largest sensory nerve in the face. This nerve is responsible for transmitting sensation from the face, eyes, nose, and mouth back to the brain. It splits into three major branches, with the lower two branches covering the teeth, gums, and oral mucosa, while the upper branch covers the nasal cavity and forehead.
The sneeze reflex is an involuntary, rapid-fire event triggered when the Trigeminal nerve detects an irritant within the nasal lining. The nerve sends a signal to the brainstem, which then coordinates the complex motor actions necessary for a sneeze. When brushing your teeth, the mechanical stimulation or the chemical sensation from the toothpaste activates the branches of the Trigeminal nerve in the mouth.
In some individuals, the neural pathways of the Trigeminal nerve are positioned in such close proximity that the intense stimulation in the mouth branch “spills over” or cross-activates the adjacent branch that serves the nasal lining. This neurological cross-talk causes the brain to incorrectly perceive the oral sensation as an irritation inside the nose, initiating the full sneeze response. This phenomenon is similar to a short circuit in a wiring system, where the electrical current meant for one component accidentally energizes a neighboring component.
Other Examples of Neurological Cross-Talk
The sneeze while brushing is one of several examples of neurological cross-talk, where stimuli from one part of the body mistakenly activate a reflex in another. One well-known example is the Photic Sneeze Reflex, often called the sun sneeze or ACHOO syndrome, which affects up to 35 percent of the population. This reflex causes a person to sneeze upon sudden exposure to bright light.
The mechanism for the photic sneeze is hypothesized to involve the summation of signals between the optic nerve, which detects the light, and the Trigeminal nerve. As the optic nerve reacts to the change in light intensity, its signal is thought to momentarily “bleed” into the adjacent Trigeminal pathway in the brainstem, triggering the sneeze. Another instance is Gustatory Rhinitis, which causes a runny nose (rhinorrhea) after eating certain foods, particularly hot or spicy ones.
This type of rhinitis is caused by the stimulation of Trigeminal sensory nerve endings, which then activates a parasympathetic reflex. These different reflexes demonstrate a broader pattern where the body’s wiring, particularly involving the Trigeminal nerve, can confuse sensory input. This confusion leads to a reflexive reaction that seems unrelated to the initial stimulus.
Is Sneezing While Brushing Normal
Sneezing when brushing your teeth is considered a normal physiological variation and is generally no cause for concern. It is simply a quirk of anatomy related to how easily your facial nerves are stimulated. The phenomenon is a benign manifestation of an easily stimulated Trigeminal nerve pathway and does not indicate any underlying health issue.
However, if brushing causes severe, sharp, or electric-shock-like pain in the face, consult a healthcare provider. Such painful sensations could be a sign of Trigeminal Neuralgia, a separate and treatable condition where the nerve is irritated, often by a blood vessel.