Dogs get teary eyes for the same basic reasons you do: irritation, allergies, blocked drainage, or an underlying eye problem. Tears are a normal part of how a dog’s eyes stay lubricated and protected, but when you notice visible wetness, streaking down the face, or discharge collecting in the corners, something is causing either too many tears or not enough drainage. Most causes are mild and manageable, though a few warrant prompt attention.
How Tear Drainage Works in Dogs
A dog’s eyes constantly produce a thin film of tears to keep the surface moist and flush away debris. In a healthy dog, most of those tears drain through a system called the nasolacrimal duct, a narrow tube that runs from the inner corner of each eye down through the skull and empties near the nose. In dogs with normal skull proportions, this duct is roughly 76 to 117 mm long and follows a gently descending path that lets tears flow by gravity. There’s also a small secondary opening near the upper canine teeth that serves as a backup drain.
When this system works properly, you never see tears on your dog’s face. When something blocks the duct, narrows it, or causes the eyes to produce more tears than the duct can handle, the overflow spills onto the fur. That visible wetness or staining is called epiphora.
Allergies and Environmental Irritants
Seasonal allergies are one of the most common reasons for watery eyes in dogs. Pollen, dust, mold spores, and even aerosolized household products like air fresheners, cleaning sprays, and perfumes can trigger an allergic response that ramps up tear production. Unlike humans, who tend to sneeze and get congested, dogs often show allergies through their skin and eyes first.
If your dog’s eyes water mainly during certain seasons, after walks in grassy areas, or after you’ve cleaned the house, environmental irritation is a likely culprit. The discharge from allergies is typically clear and watery rather than thick or colored.
Eyelid and Eyelash Abnormalities
Some dogs are born with structural quirks around the eyes that cause chronic tearing. The two most common are entropion and distichiasis.
Entropion is a condition where the eyelid rolls inward, pressing the eyelid skin and lashes directly against the surface of the eye. This constant contact irritates the cornea and triggers a reflexive flood of tears. It can affect one or both eyes and tends to run in certain breeds.
Distichiasis means extra eyelashes growing from the wrong spot, specifically from the oil gland openings along the eyelid margin. These misplaced lashes can be thick or fine, pigmented or nearly invisible. When they’re soft and wispy, a dog may show no symptoms at all. But stiffer lashes that rub against the eye cause watering, redness, and irritation. Dogs with distichiasis often rub their faces on carpet or paw at their eyes. In English Bulldogs, both entropion and distichiasis each affect more than 10% of the breed.
Flat-Faced Breeds and Tear Overflow
Brachycephalic breeds, dogs with shortened snouts and flattened faces, are especially prone to teary eyes. Pugs, French Bulldogs, English Bulldogs, Shih Tzus, Pekingese, and Lhasa Apsos all fall into this category. Their compressed skull shape distorts the tear drainage system in several ways.
In a normal dog, the nasolacrimal duct follows a gentle, L-shaped curve. In flat-faced dogs, the duct bends into more of a U shape because the bones of the face are so compressed. The tear collection sac near the inner eye, which normally has a distinct teardrop shape, is often shrunken and hard to identify in brachycephalic breeds. These structural changes make it physically harder for tears to drain, so they spill over onto the face instead. On top of the drainage problems, these breeds are also more likely to develop corneal ulcers, dry eye, and other conditions that trigger extra tear production in the first place.
What Tear Stain Color Tells You
The color of the discharge around your dog’s eyes is one of the most useful clues to what’s going on. Clear, watery tears that leave reddish-brown streaks on the fur are usually not a sign of infection. That discoloration comes from porphyrins, iron-containing molecules produced when the body breaks down red blood cells. Tears naturally contain porphyrins, and when they sit on fur, especially light-colored fur, they oxidize and leave a rust-colored stain. Some dogs simply produce more porphyrins than others, which is why tear staining varies even among dogs of the same breed.
Yellow or green discharge is a different story. That color typically signals a bacterial infection, whether from conjunctivitis, an infected scratch, or a deeper eye problem. Thick, mucus-like discharge that crusts around the eyes also points toward infection or chronic inflammation rather than simple overflow.
Blocked Tear Ducts
Sometimes the drainage system itself is the problem. Hair growing near the inner corner of the eye can physically block the entrance to the nasolacrimal duct. Debris, mucus, or inflammatory material can also form a plug inside the duct. In some dogs, the duct narrows over time due to scarring from past infections or inflammation.
For straightforward blockages, a vet can flush the duct with sterile saline under sedation, which often clears the obstruction. For more stubborn cases involving scarring or structural narrowing, a small stent (a thin tube) can be placed inside the duct to hold it open. In one study of dogs that had failed standard flushing, stent placement for a median of about five and a half weeks led to owners reporting a median 95% improvement in symptoms, with half of the dogs experiencing complete resolution.
More Serious Causes
While most teary eyes are harmless, excessive tearing can sometimes signal a condition that needs treatment sooner rather than later.
- Corneal ulcers are open sores on the surface of the eye, often caused by a scratch, a foreign body, or chronic irritation from misplaced lashes. Signs include watery eyes combined with spasmodic squinting, visible cloudiness or a white spot on the eye, and sensitivity to light. Untreated ulcers can deepen and lead to serious complications.
- Glaucoma involves a dangerous buildup of pressure inside the eye. It causes pain, excessive tearing, a visibly enlarged or bulging eye, and redness. Glaucoma can damage vision permanently if not caught early.
- Anterior uveitis, inflammation of the structures behind the cornea, causes tearing along with a constricted pupil, redness, squinting, and light sensitivity. It sometimes develops as a complication of other eye diseases.
The common thread with serious conditions is that tearing is accompanied by other symptoms: squinting, pawing at the eye, cloudiness, swelling, or behavioral changes like lethargy or loss of appetite. Watery eyes alone, without those red flags, are far less likely to indicate an emergency.
How Vets Find the Cause
A veterinary eye exam for tearing is straightforward and painless. The two most common tests are the Schirmer tear test and fluorescein staining. The Schirmer test involves placing a small strip of absorbent paper inside the lower eyelid for about a minute to measure how much tear fluid the eye produces. This helps determine whether the problem is overproduction or poor drainage. Fluorescein staining uses a drop of orange dye on the eye’s surface that highlights scratches, ulcers, or other damage under a special light. If a blocked duct is suspected, the vet may flush saline through the duct to see whether it drains normally.
These tests together give a clear picture of whether the issue is structural, infectious, allergic, or something else entirely, which determines whether your dog needs medication, a minor procedure, or simply regular face cleaning to manage staining.