When tears well up and your nose begins to sting, it is a common sensation. This experience results from the intricate connection between your eyes and nasal passages. Understanding the physiological processes behind crying helps explain this stinging feeling.
The Tear Drainage System
Tears originate in the lacrimal glands, located above the outer corner of each eye. These glands produce tears that spread across the eye’s surface, keeping it moist and protected. After lubricating the eye, tears enter a specialized drainage system instead of overflowing onto the cheeks.
Tears collect near the inner corner of the eye and enter tiny openings called puncta, found on both the upper and lower eyelids. From the puncta, tears flow into small channels called canaliculi, leading to the lacrimal sac, a reservoir situated beside the upper part of the nose. The lacrimal sac narrows into the nasolacrimal duct, which descends through the bone and opens into the nasal cavity, specifically into the inferior meatus. This system drains excess tears into the nose, preventing them from spilling over the eyelids.
Why Tears Irritate Nasal Passages
The stinging sensation in the nose during crying arises from the chemical composition of tears interacting with the delicate lining of the nasal passages.
Tears are primarily water, but they contain electrolytes like sodium, potassium, calcium, and magnesium. Sodium chloride, or common salt, contributes to the salty taste of tears, with a concentration similar to blood plasma (around 0.9%). When these salty tears reach the nasal cavity, they irritate the mucous membranes lining the nose.
The pH of tears (6.5 to 7.6) is slightly different from the normal pH of the nasal lining. This pH imbalance, combined with electrolytes, can further contribute to the irritating effect on the sensitive nasal tissues.
The nasal lining is richly supplied with sensory nerve endings, particularly branches of the trigeminal nerve, making it responsive to various stimuli. These nerve endings detect the irritating properties of tears, sending signals interpreted as a stinging or burning sensation.
The Body’s Response to Crying
The act of crying itself triggers several physiological responses in the body that intensify the nasal sensation. When crying, there is an increase in blood flow to the face and nasal passages. This heightened blood flow can cause the nasal membranes to swell, leading to a feeling of congestion and increased sensitivity within the nose.
The influx of tears into the nasal cavity combines with the naturally produced mucus in the nose. This mixture can increase the overall fluid volume, leading to a runny nose. The combination of irritated nasal membranes from tear composition and the physical changes like swelling and increased mucus production creates the noticeable stinging and discomfort commonly experienced during crying.