Why Do I Cry Out of One Eye? Causes and What to Do

Tearing from just one eye usually points to a physical difference between your two eyes rather than anything happening in the brain’s emotional circuits. The most common culprit is a partial or full blockage in the tiny drainage channel on the affected side, though infections, nerve problems, and even certain medications can produce the same lopsided tears. Because the causes range from harmless to worth investigating promptly, understanding what drives the asymmetry helps you figure out whether you need a warm compress or an eye doctor’s appointment.

How Tears Normally Drain

Your eyes produce tears constantly, not just when you cry. A thin film of fluid coats each eye to keep the surface moist, wash away debris, and deliver nutrients. Sensory nerves in the cornea detect dryness or irritation and trigger a reflex that tells the lacrimal gland to ramp up tear production.¹ Parasympathetic and sympathetic nerves fine-tune how much water, salt, and protein the gland releases onto the eye’s surface.²

Once tears have done their job, they don’t just evaporate. Most of the fluid drains through two tiny openings called puncta, one on each eyelid near the inner corner of the eye. From there, the tears travel through short channels (canaliculi), collect in a small pouch called the lacrimal sac, and flow down the nasolacrimal duct into your nose. That’s why your nose runs when you cry. If anything narrows or blocks that plumbing on one side, tears back up and spill over the lower lid of that eye only.

Blocked Nasolacrimal Duct, the Most Common Structural Cause

A blocked nasolacrimal duct is one of the most frequent reasons adults and children develop persistent tearing from a single eye. The blockage causes tear fluid to pool in the lacrimal sac instead of draining into the nose, and the overflow runs down your cheek. Along with constant watering, you may notice a sticky or mucus-like discharge, especially in the morning.³

In babies, the blockage is usually congenital. The duct simply hasn’t finished opening by the time the child is born, with the obstruction most often sitting at the valve of Hasner where the duct meets the inside of the nose.³ Parents typically notice one eye that waters nonstop while the other stays dry. The good news is that most of these open on their own within the first year, often with the help of gentle massage over the lacrimal sac.

In adults, the blockage develops over time. It can result from chronic low-grade inflammation, scar tissue from a sinus infection, nasal polyps, trauma to the nose or cheek, or simply age-related narrowing of the duct. Women are affected more often than men, possibly because the bony canal that houses the duct tends to be narrower in female anatomy. The nasolacrimal duct itself is the most common site of acquired obstruction.³

Infections and Inflammation That Affect One Eye

Conjunctivitis, the classic “pink eye,” can strike one eye before the other or sometimes stay confined to a single eye entirely. Viral conjunctivitis is the most common form overall, followed by bacterial conjunctivitis as the second most frequent infectious type.⁴ Both produce watery or goopy discharge, redness, and the sensation that something is in your eye. With a viral infection, the tearing can be profuse and relentless on the affected side.

Allergic conjunctivitis, on the other hand, usually hits both eyes at once because the allergen reaches both surfaces simultaneously. However, if you rub one eye with a hand that has pollen or pet dander on it, you can trigger a one-sided reaction. The hallmarks of allergic conjunctivitis are itching, a stringy mucus discharge, and swelling of the eyelid or the clear membrane over the white of the eye.⁴ If the itch is intense and only in one eye, think about what that eye was exposed to recently.

Dacryocystitis is another infection worth knowing about. This happens when stagnant tears in a blocked lacrimal sac become a breeding ground for bacteria. The inner corner of the affected eye becomes red, swollen, painful, and warm to the touch, and pressing on the area may push pus back up through the punctum. It nearly always affects one side, because it depends on the anatomy of that particular duct.

Neurological Causes

The nerves that control tear production and the muscles around your eye can also explain one-sided tearing when no blockage or infection is present. A few conditions stand out.

Bell’s Palsy

Bell’s palsy causes sudden weakness or paralysis of the muscles on one side of the face. The affected side loses its ability to close the eyelid fully, which means the eye dries out and tears reflexively to compensate. At the same time, the lower eyelid may droop, pulling the punctum away from the eye’s surface so tears can’t drain properly. The combination of overproduction and poor drainage leads to constant watering on that side. Bell’s palsy also causes drooping of the brow and the corner of the mouth, so the one-sided tears rarely appear in isolation.⁵

Crocodile Tears Syndrome

After Bell’s palsy or another facial nerve injury heals, the regenerating nerve fibers sometimes reconnect to the wrong targets. Fibers that were supposed to control salivation end up wired to the lacrimal gland instead. The result is “crocodile tears,” where the affected eye waters every time you eat or even taste something flavorful. This was first systematically described in patients whose facial paralysis had been complete for several months; as voluntary movement returned, excessive tearing on the affected side appeared whenever the patient ate.⁶ If you notice your eye tears up only during meals, this misfiring is a likely explanation.

SUNCT and Related Headache Syndromes

A group of rare headache disorders can cause dramatic one-sided tearing that accompanies sharp, stabbing head pain. SUNCT syndrome (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing) produces bursts of severe pain around one eye along with massive tearing, redness of the white of the eye, forehead sweating, and a runny nose, all on the same side as the pain.⁷ Paroxysmal hemicrania and cluster headache share similar one-sided autonomic features, including tearing, nasal congestion, and eyelid drooping or swelling.⁸ If your one-sided tears come in episodes alongside intense pain around or behind the eye, these conditions are worth raising with a neurologist.

When Medications Are to Blame

Certain drugs can cause persistent tearing in one or both eyes by damaging the delicate lining of the tear drainage channels. The chemotherapy agents best documented to cause this are 5-fluorouracil and docetaxel, both of which can inflame and eventually scar the canaliculi, the short tubes connecting the puncta to the lacrimal sac.⁹ Other drugs reported to cause tearing include capecitabine, imatinib, radioactive iodine treatment for thyroid cancer, and a few others. The severity depends on the specific drug, the dose schedule, and the individual patient, so some people develop only mild inflammation while others end up with significant scarring that needs surgical correction.

If you’re undergoing chemotherapy and notice one eye starting to water persistently, mention it to your oncologist early. Catching canalicular inflammation before it progresses to full stenosis gives you more treatment options and better outcomes.

Congenital Differences That Cause Lifelong One-Sided Tearing

Some people are born with structural variations that affect tear drainage on only one side. Beyond the common congenital nasolacrimal duct blockage that usually resolves in infancy, there are rarer conditions. Punctal agenesis, the absence of one or both punctal openings, is one example. In a study of patients with this condition, both puncta were absent in 53 eyes while a single punctum was missing in 41 eyes. When surgeons opened the lacrimal sac in eyes missing both puncta, they found no underlying canalicular tissue in the vast majority of cases, meaning the drainage tubes simply never formed.¹⁰ Fortunately, surgical repair resolved the tearing in over 90% of operated eyes.

These congenital conditions sometimes go undiagnosed for years, especially if the tearing is mild or intermittent. A person might grow up thinking one eye just “waters more” without realizing there’s a fixable anatomical reason. If you’ve had one-sided tearing for as long as you can remember, it’s worth getting the drainage system checked, because these issues tend not to resolve on their own.

Dry Eye, the Counterintuitive Culprit

It sounds backward, but a dry eye can actually be the eye that tears the most. When the baseline tear film is thin or breaks up too quickly, the cornea’s sensory nerves register irritation and trigger a flood of reflex tears. These emergency tears are watery and thin, lacking the oily top layer that keeps normal tears from evaporating. So the eye cycles between feeling gritty and dry, then suddenly overflowing with tears that don’t stick around long enough to help. If the dryness is worse on one side, perhaps because of a drafty office setup, a ceiling fan blowing from one direction, or a habit of sleeping with one eye slightly open, you’ll notice the reflex tearing on that side.

Wind, air conditioning, prolonged screen time, and contact lens wear are all common triggers that can worsen one eye more than the other depending on your environment and anatomy. Preservative-free artificial tears can help stabilize the tear film and reduce the reflex flooding. If over-the-counter drops don’t help after a few weeks, an eye doctor can test your tear production and quality more precisely.

What You Can Do at Home

Before you book a specialist appointment, a few practical steps can help you figure out what’s going on and may even fix mild cases:

• Warm compresses: A warm, damp cloth held against the inner corner of the affected eye for five to ten minutes can soften debris in the drainage channels and relieve mild blockages. Repeat two to three times a day.
• Lacrimal sac massage: For babies with congenital duct blockage, and sometimes for adults with partial blockages, gently pressing and sliding a finger downward over the lacrimal sac area (between the inner corner of the eye and the side of the nose) can help push fluid through and encourage the duct to open.
• Artificial tears: If reflex tearing from dryness is the issue, preservative-free drops used regularly throughout the day can reduce the irritation cycle that triggers overflow tears.
• Environmental adjustments: Redirect fans and vents away from your face, take screen breaks to blink more often, and use a humidifier if indoor air is dry. These changes can be surprisingly effective when dry-eye-driven tearing is the problem.

Medical and Surgical Treatments

When home remedies aren’t enough, several office-based and surgical procedures target the specific cause of one-sided tearing.

For nasolacrimal duct blockage in children, probing the duct with a thin wire is the standard first-line treatment. In children under three years old, probing successfully opens the duct in roughly three out of four cases, with no decline in success rates as the child ages within that window.¹¹ The procedure is quick and usually done under brief general anesthesia for young children.

For adults with confirmed duct blockage, probing is also a reasonable first step. It offers relatively good results and high patient satisfaction, and it doesn’t compromise future surgical options if it doesn’t work.¹² One prospective trial found that adding a low dose of mitomycin C during the probing procedure increased the success rate, though failure rates climbed with patient age.¹³

If probing fails or the blockage is severe, dacryocystorhinostomy (DCR) is the gold standard surgery. This procedure creates a new pathway between the lacrimal sac and the nasal cavity, bypassing the blocked duct entirely. It can be performed externally through a small skin incision near the side of the nose or endoscopically through the nostril with no visible scar. Success rates for DCR are high, generally above 90% in experienced hands, and the relief from chronic tearing is usually permanent.

For tearing caused by punctal or canalicular stenosis from chemotherapy, treatment depends on how far the scarring has progressed. Early inflammation may respond to stopping or adjusting the offending drug, along with punctal dilation. Advanced scarring may require surgical bypass, such as placing a tiny glass tube (a Jones tube) that runs from the inner corner of the eye directly into the nasal cavity.

When to See a Doctor

Most one-sided tearing is annoying but not dangerous. A visit to an eye specialist is a good idea if:

• Tearing persists beyond two weeks: A brief episode from a stray eyelash or a cold is normal. Ongoing watering suggests something structural or inflammatory.
• Discharge is thick, yellow, or green: This points to bacterial infection, possibly dacryocystitis, which may need antibiotics.
• You have pain, redness, or swelling near the inner corner: Acute dacryocystitis can progress to a more serious infection if untreated.
• Tearing accompanies facial weakness: One-sided facial drooping with eye watering suggests Bell’s palsy or another nerve issue that benefits from early treatment.
• Episodes come with severe headache: The combination of stabbing pain around the eye with tearing, redness, and nasal congestion suggests a trigeminal autonomic headache that a neurologist should evaluate.
• You’re on chemotherapy: Early detection of canalicular damage gives the best chance of preserving normal drainage.

Can Emotional Crying Affect One Eye More Than the Other?

Emotional tears are generated by both lacrimal glands simultaneously, so in theory, both eyes should tear equally when you’re sad or moved. In practice, slight anatomical differences between your two drainage systems mean one eye may overflow before the other. If the left nasolacrimal duct drains a tiny bit more efficiently than the right, the right eye fills up and spills first. This doesn’t indicate any medical problem. It’s just a quirk of your personal plumbing. Nearly everyone who pays attention during a good cry will notice one eye leads the way.

Where it gets more interesting is if emotional crying consistently produces tears from only one eye with the other staying completely dry. That pattern could hint at reduced lacrimal gland function on the dry side, possibly from prior surgery, radiation, or an autoimmune condition affecting one gland more than the other. It’s uncommon but worth mentioning to an eye doctor if you notice it reliably.

Why Wind and Cold Air Trigger One Eye

If your eye only waters when you step outside into wind or cold, you’re experiencing a normal protective reflex that happens to be stronger on one side. Cold, dry air evaporates the tear film faster, and wind hits the cornea directly, stimulating the trigeminal nerve’s sensory endings. The reflex response is a burst of watery tears. The reason it strikes one eye more is usually that one punctum sits slightly differently, one eyelid closes less tightly, or one side of your face catches the breeze more squarely. Wearing wraparound sunglasses on windy days cuts the stimulus and stops the reflex before it starts. If the tearing is excessive even in mild conditions, though, it may be layered on top of an underlying drainage issue or dry-eye condition that’s worth addressing separately.