Excessive tearing, medically known as epiphora, is a common symptom that frequently accompanies a cold or flu. This issue is a consequence of complex physiological reactions to a pathogen. Understanding the biological reasons involves looking at how the eye’s plumbing system interacts with the inflammatory response of a respiratory illness, causing a temporary imbalance in tear production and drainage.
The Tear System: Production and Drainage
Tears are produced primarily by the lacrimal glands, located above the outer corner of each eye. These glands continuously secrete the watery component of the tear film, which is spread across the eye’s surface with every blink. This fluid lubricates the eye, provides oxygen, and washes away debris. Tears gather at the inner corner before draining through two tiny openings called puncta. The puncta lead into small tubes connecting to the lacrimal sac, which ultimately empties into the nasolacrimal duct, channeling tears into the nasal cavity.
The Primary Mechanisms of Sickness-Induced Watering
The excessive watering experienced when sick is due to a combination of two distinct mechanical problems: overproduction and under-drainage.
Overproduction (Reflex Tearing)
The first mechanism involves reflex tearing, where inflammation on the eye’s surface acts as an irritant. When the conjunctiva, the transparent membrane covering the white of the eye, becomes inflamed due to illness, it sends a signal to the nervous system. This signal stimulates the lacrimal glands to dramatically increase tear output in an attempt to flush away the irritant.
Under-Drainage (Physical Blockage)
The second mechanism is a physical blockage of the tear drainage pathway. The nasolacrimal duct passes through the bony structure of the face and opens directly into the nasal cavity. When an infection causes the mucous membranes lining the nose and sinuses to swell, the internal opening of this duct can become narrowed or obstructed. This congestion prevents tears from draining normally into the nose, causing them to back up, pool in the eye, and spill over the eyelid.
The underlying inflammatory process links both mechanisms. The body’s immune response to a virus releases inflammatory mediators that cause tissue swelling and dilation of blood vessels. This inflammation irritates the ocular surface, triggering overproduction, and causes surrounding tissues in the nasal passages to become engorged. This engorgement compresses the tear duct, leading to temporary drainage failure that results in epiphora.
Common Illnesses and Specific Triggers
Upper respiratory infections, such as the common cold caused by rhinoviruses, are the most frequent culprits for sickness-induced watery eyes. The viral infection targets the mucous membranes lining the entire respiratory tract, including the tissue surrounding the nasolacrimal duct. This widespread inflammation leads to the characteristic nasal congestion and sinus swelling that mechanically obstructs the tear drainage system.
Influenza and other respiratory viruses operate through similar inflammatory pathways, causing significant swelling in the nasal cavity. Congestion is often worse when lying down, which can exacerbate tear duct compression and lead to more noticeable watering at night or upon waking. Sinus infections, whether viral or bacterial, produce deep inflammation that can also block the duct, causing tears to stagnate and sometimes leading to secondary eye irritation.
Allergies, while not an illness, trigger the same hyper-inflammatory response that affects the tear system. Allergic reactions release histamine, which causes inflammation and swelling in the nasal passages and on the conjunctiva. This swelling mimics the effects of a cold, irritating the eye to produce more tears while also narrowing the nasolacrimal duct. Both infectious and non-infectious inflammatory triggers can temporarily overwhelm the eye’s drainage capacity.
When to Seek Medical Attention
While watery eyes are a typical symptom of a common cold, certain accompanying signs suggest a more serious condition requiring professional evaluation. Consult a healthcare provider if the excessive tearing is accompanied by changes in vision, such as blurriness or decreased sight. Severe pain in or around the eye is another sign that the problem may be more than simple congestion.
The presence of thick, colored discharge, especially yellow or green pus, warrants medical attention. This can indicate a bacterial infection like conjunctivitis or a tear duct infection called dacryocystitis. Seek an examination if you feel a persistent sensation that a foreign object is stuck in your eye, or if your eyes are extremely sensitive to light. If the watering persists long after the other cold symptoms have resolved, it may suggest a chronic blockage that needs treatment.