Causes of One Tearing Eye

Tearing from one eye generally suggests a different list of possible causes compared to when this symptom affects both eyes. One-sided tearing typically arises due to overproduction or impaired drainage of tears in the affected eye. A variety of conditions can cause this symptom and medical evaluation is needed to accurately determine the cause and best treatment options.

Eyeball Scratch or Foreign Body

Getting something in your eye typically leads to sudden, one-sided tearing. This often causes a scratch on the eyeball surface with associated discomfort, watering and redness. Although the culprit is often obvious, such as a bit of dirt or sand, this might not always be the case. For example, you might have a stray inward-growing eyelash that scratches the eyeball surface with each blink. A superficial eyeball scratch -- known medically as a corneal abrasion -- can also occur in the absence of a foreign body in your eye. An accidental poke in the eye or wearing a dirty or torn contact lens are common culprits. Seek medical care right away for persistent tearing, especially if you continue to feel as though something is in your eye.

Blocked Tear Drainage

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Persistent, one-sided eye tearing often signals a blockage somewhere in the tear drainage system, also known as the nasolacrimal drainage system. Many conditions can lead to such a blockage, including:

• Infection, often with staph or strep bacteria
  
• Age-related constriction of the tear ducts
• Blocked tear duct openings due to debris from eyelid flaking or cosmetics
• Nasolacrimal polyps or tumors
• A nasolacrimal stone, or dacryolith
• Eye, eyelid or facial trauma, such as a broken nose

Medical evaluation and diagnosis are needed as treatment for a blockage of the nasolacrimal system depends on the underlying cause.

Eyelid Conditions

Several eyelid conditions can lead to one-sided eye tearing. Infectious or noninfectious blockage of an oil gland in an upper or lower eyelid -- known as a hordeolum or stye, and chalazion, respectively -- gives rise to a tender lump on the eyelid, which is often accompanied by some tearing. Application of warm compresses to the affected eye several times daily usually clears these blockages.

Abnormal inward or outward rotation of the upper or lower eyelid often disrupts the balance between tear production and drainage leading to a watery eye. Causes of this condition when affecting only one eye include:

• Bell palsy, a condition causing temporary weakness or paralysis of the muscles on one side of the face
• A stroke that causes weakness or paralysis of muscles on one side of the face
• Scarring from past eyelid injury or surgery
• A noncancerous, precancerous or cancerous eyelid growth
  

Other Considerations, Warnings and Precautions

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The conditions discussed cover many, but not all, of the possible causes of one-sided eye tearing. For example, people with migraines sometimes experience this symptom. Eye tearing can also occur along with other symptoms with shingles affecting the eye, a sight-threatening condition. See your doctor for any unexplained, persistent eye tearing. Seek emergency medical care if a cleaner or other chemical accidentally splashes into your eye, or if you experience any warning signs or symptoms including:

• Sudden weakness or paralysis of the facial muscles on one side of your face
  
• Burning, tingling, itchiness and/or a rash on one side of your forehead or surrounding one eye
• Severe or worsening eye pain
• Sudden change in your vision

Reviewed and revised by: Tina M. St. John, M.D.