Epiphora, the medical term for excessive tearing, is a common and frustrating symptom where tears spill onto the cheek without an apparent trigger like sadness or injury. This condition represents an imbalance between the rate of tear production and the eye’s ability to drain them effectively. When watering eyes occur for no obvious reason, it often points to a subtle underlying physical or systemic issue affecting the tear system. Understanding these causes is the first step toward finding relief.
The Paradox of Reflex Tearing
One of the most common, yet counterintuitive, reasons for watery eyes is chronic dry eye disease, medically known as keratoconjunctivitis sicca. When the surface of the eye is too dry or the tear film quality is poor, the brain registers this irritation and signals an emergency response. This response is known as reflex tearing, where the main lacrimal gland produces a sudden flood of watery tears to flush out the perceived irritant.
The tear film is a complex structure composed of three layers: an inner mucus layer, a thick middle aqueous (watery) layer, and a thin outer lipid (oil) layer. In many cases of dry eye, the lipid layer, secreted by the meibomian glands, is deficient. Without this oil, the aqueous layer evaporates too quickly, leading to instability and dryness.
The emergency tears produced during reflex tearing are predominantly aqueous, lacking the necessary oils for proper lubrication. Because they are thin and watery, they drain poorly, which leads to the overflow onto the cheek. This creates a frustrating cycle where an eye that is fundamentally dry is constantly watering.
Issues with Tear Drainage
Tears normally exit the eye through a precise drainage system, and a malfunction in this system is a frequent cause of unexplained tearing. Tears are collected by two tiny openings, called puncta, located in the inner corner of the upper and lower eyelids. They then travel through small tubes called canaliculi, into the lacrimal sac, and finally down the nasolacrimal duct into the nasal cavity. A physical obstruction at any point along this path, known as nasolacrimal duct obstruction, prevents the tears from draining, causing them to pool and spill over the eyelid margin. In adults, this blockage is often caused by inflammation, scarring from previous infections, age-related narrowing of the duct, or, rarely, a tumor. Even a complete blockage of the tiny punctal openings can occur, which completely halts the initial collection of tears.
Eyelid Structural Problems
Structural problems with the eyelids themselves can disrupt the tear drainage process. Ectropion is a condition where the lower eyelid turns outward and away from the eye, typically due to age-related tissue laxity. This malposition prevents the eyelid from making proper contact with the eyeball and misaligns the punctum, making it impossible for the eyelid’s pumping action to direct tears into the drainage system. Conversely, entropion, where the eyelid turns inward, causes the eyelashes to rub against the cornea, leading to irritation and a reflex production of tears that then cannot drain properly due to the structural disarray.
External Irritants and Inflammation
The eyes are highly sensitive organs, and excessive tearing can be a direct, protective response to acute environmental factors and low-grade inflammation. This is the body’s natural defense mechanism, working to wash away anything perceived as a threat to the ocular surface. Airborne irritants, such as pollen, dust, and pet dander, can trigger allergic conjunctivitis, causing mast cells to release inflammatory chemicals that result in itching and copious, watery tears.
Exposure to harsh environmental conditions, even without direct allergens, can provoke this reflex tearing. Strong wind, smoke, chemical fumes, or prolonged exposure to dry, cold air can irritate the eye’s delicate surface. The eye reacts to this irritation by initiating a sudden flow of tears, which may appear to be “for no reason” if the irritant is not immediately visible.
Persistent, low-level inflammation of the eyelids, such as blepharitis, can also cause chronic irritation that leads to excessive watering. Blepharitis involves oil gland dysfunction at the eyelid margins, which constantly irritates the eye, prompting a continuous, low-grade reflex tear production. Similarly, a mild case of conjunctivitis or the presence of a stye or chalazion can create enough irritation to keep the lacrimal gland in an overproduction state.
Systemic and Emotional Triggers
In some instances, the source of unexplained tearing is not a local eye problem but a malfunction in the nervous system that controls tear production. One such condition is Pseudobulbar Affect (PBA), a neurological disorder characterized by sudden, frequent, and uncontrollable episodes of crying or laughing that are inappropriate to the person’s actual emotional state. These episodes are caused by damage to brain pathways that regulate emotional expression, often seen in individuals with conditions like stroke, multiple sclerosis, or traumatic brain injury. While the person may not feel sad, the brain’s expressive pathway triggers the physical act of crying, leading to involuntary tear production.
Another unusual neurological cause is gustatory epiphora, often called “crocodile tears syndrome.” This is a rare complication following facial nerve recovery where the nerves that stimulate the salivary glands become miswired to the lacrimal gland, causing tearing while eating.
Emotional and psychological factors can also play a subtle role in chronic tearing. High levels of chronic stress, anxiety, or fatigue can increase sensitivity to minor irritants. While not a direct cause of reflex tearing, these systemic factors can amplify the body’s physical responses, making the eyes more prone to watering.