When a cold, the flu, or other infections strike, watery eyes—medically known as epiphora—are a common side effect. This excessive tearing is a response from the body’s respiratory and immune systems working together to combat the illness. The phenomenon results from two distinct physiological processes: mechanical tear drainage blockage and the biological action of the immune response. Understanding these mechanisms explains why tears often stream down your face when you are unwell.
Blockage of Tear Drainage Pathways
The primary mechanical reason for watery eyes during an illness is the temporary obstruction of the tear drainage system. Tears are constantly produced by the lacrimal glands to lubricate the eye surface. They normally drain through tiny openings called puncta, located in the inner corners of the eyelids, flowing into canals that lead to the nasolacrimal duct. This duct connects the eye area to the nasal cavity, carrying tears down into the nose.
When a person has a respiratory infection, the mucous membranes lining the nasal passage become inflamed and swell. This inflammatory swelling constricts the space within the nasal cavity, physically squeezing the nasolacrimal duct.
The blockage prevents tears from draining normally into the nose, causing them to back up and pool on the eye surface. They spill over the lower eyelid and onto the cheek, creating the watery-eye effect. The severity of the tearing often worsens as nasal congestion increases, especially when lying down.
Inflammation and Immune Response
Separate from the drainage issue, the immune system’s fight against pathogens also causes excessive tearing. When a virus enters the body, the immune system releases chemical mediators like histamines to combat the infection. These chemicals increase blood flow and cause inflammation throughout the affected areas, including the tissues surrounding the eyes.
Systemic inflammation can directly irritate the conjunctiva, the thin membrane covering the eye and inner eyelids. This irritation often leads to conjunctivitis, characterized by redness, discomfort, and a reflexive overproduction of tears. These reflex tears attempt to flush out irritants or infectious agents from the eye’s surface.
In some cases, the virus can directly infect the eye tissue, stimulating the lacrimal glands to produce a greater volume of tears. This increased tear volume, combined with decreased drainage capacity, ensures the tears overflow. This mechanism protects the eye, even though the watery eyes are inconvenient.
When Tearing Requires Medical Attention
While watery eyes are usually a harmless symptom of a cold or flu, certain signs warrant a medical evaluation. Excessive tearing that resolves as the illness passes is not a concern. However, if symptoms persist longer than the main illness (more than 7 to 10 days), it is prudent to seek advice, as prolonged tearing could indicate a persistent blockage or a secondary infection.
Specific accompanying symptoms require immediate attention from a physician or eye doctor. These include any noticeable change in vision, such as blurriness or loss of sight, or the onset of severe pain around the eyes. The presence of thick, yellowish-green discharge, rather than clear tears, suggests a bacterial infection, potentially leading to complications like dacryocystitis.
Other red flags are extreme sensitivity to light, unexplained bruising around the eye, or tenderness and swelling near the nose or sinuses. These symptoms, especially when combined with a fever, suggest a serious localized infection or inflammation that may require specific treatment, such as antibiotics. Consulting a healthcare provider ensures the tearing is correctly attributed to the passing illness and not a significant underlying eye condition.