When a cold or allergy strikes, the typical response is a runny nose and watery eyes on both sides of the face. Having a runny eye and nostril confined strictly to one side, known medically as unilateral epiphora and rhinorrhea, is a distinct phenomenon. This presentation suggests a localized issue rather than a systemic one. Understanding why only one side is affected requires looking at the specialized drainage system that links the eye and the nose. This singular presentation points toward a specific anatomical problem or a highly localized irritant affecting the drainage pathway.
The Anatomical Connection Between the Eye and Nose
The reason a problem in the eye can cause drainage in the nose lies in a specialized structure called the nasolacrimal duct system. This system acts as the body’s plumbing, designed to drain excess tears and fluid from the eye’s surface into the nasal cavity. Tear fluid is constantly produced to lubricate and protect the eye, and this fluid must be continuously removed.
Tears collect near the inner corner of the eye and enter tiny openings called the puncta, located on the upper and lower eyelids. From the puncta, the tears flow through small canals, called the canaliculi, into the lacrimal sac, positioned next to the nose. The lacrimal sac then funnels the fluid downward into the nasolacrimal duct, which passes through a bony channel and empties directly into the lower part of the nasal cavity. This drainage explains why crying often leads to a runny nose and why certain eye drops can be tasted in the throat.
The entire duct system functions as a one-way street, connecting the eye to the nasal passage on each side independently. This separation allows a localized issue, such as a blockage or inflammation, to interrupt drainage on only one side. When the flow is impeded, tears back up, causing the watery eye. The backed-up fluid can sometimes mix with nasal mucus, contributing to the unilateral runny nostril.
Common Causes of Unilateral Eye and Nose Discharge
The most frequent explanation for unilateral symptoms is a mechanical obstruction of the nasolacrimal duct, known as dacryostenosis. This blockage prevents the normal flow of tears and is common in adults due to age-related narrowing, scar tissue from prior infections, or inflammation. When the drainage pathway is physically blocked on one side, tears spill over the eyelid and drain toward the nostril.
A localized infection within the drainage system, known as dacryocystitis, also accounts for many unilateral cases. This infection occurs when bacteria colonize stagnant fluid in a blocked lacrimal sac, leading to inflammation, pain, and purulent discharge from the eye. The resulting pressure and inflammation can irritate the adjacent nasal lining, increasing mucus production and causing one-sided nasal drainage. Since the infection is contained within the sac on one side, the opposite eye and nostril remain unaffected.
Unilateral symptoms can also arise from structural issues within the nasal cavity, such as a nasal polyp or a severely deviated septum. These conditions can physically compress the nasolacrimal duct’s opening where it enters the nose, creating a functional blockage. The constant pressure impedes tear drainage even if the rest of the duct system is clear. This leads to chronic unilateral tearing that manifests as a runny eye and a corresponding runny nose.
Even common irritants can cause unilateral discharge if the exposure is asymmetric. For example, sleeping with one side of the face pressed into a pillow that has collected allergens, or having a foreign body lodged in one eye, can trigger a localized tearing response. The body’s attempt to wash out the irritant results in an overproduction of tears that overwhelms the drainage system. This leads to temporary unilateral symptoms.
Recognizing When the Cause is Serious
While most instances of one-sided discharge relate to common blockages or infections, certain accompanying signs suggest a more concerning underlying issue. Symptoms that persist for longer than two weeks, or those that suddenly worsen, warrant prompt medical evaluation. This is particularly true if the discharge is accompanied by severe pain in the area between the eye and the nose.
A serious infection may be indicated by a high fever or noticeable, firm swelling and redness that extends beyond the immediate corner of the eye. Any discharge that is bloody or has a foul odor should be investigated by a physician. In rare instances, a mass or tumor in the nasal cavity or sinus can press on the nasolacrimal duct. Its presence may be suggested by progressive symptoms, facial numbness, or changes in vision.
Changes in visual acuity, such as blurriness or double vision, or pain upon moving the affected eye are signs that the infection or inflammation may be spreading deeper into surrounding tissues. Consulting with an ophthalmologist or an otolaryngologist is recommended if these warning signs appear or if the unilateral discharge does not resolve with simple care. These specialists can perform specific tests to determine if the cause is a simple obstruction or a condition requiring intervention.