What to Do If a Dog Has Watery Eyes: A Science-Based Guide
Learn what to do if a dog has watery eyes — from tear production science to breed-specific risks, home care steps, and when to see the vet.
Quick Answer: What to Do If a Dog Has Watery Eyes
If your dog has watery eyes, start by gently wiping the area with a clean, damp cloth or sterile saline eyewash. Check for visible irritants like dust, grass seeds, or hair. Monitor for 24 hours. If the discharge turns yellow, green, or bloody, or if your dog is squinting, pawing at the eye, or the eye appears swollen or cloudy, contact your veterinarian immediately. Clear, occasional tearing is often normal — persistent or colored discharge is not.
The Science of Canine Tear Production
Dog tears are produced by two primary structures: the lacrimal gland (located above the outer corner of the eye) and the nictitans gland (embedded in the third eyelid, or nictitating membrane). Together, these glands produce the aqueous layer of the tear film — the watery middle layer that keeps the cornea nourished, oxygenated, and free of debris.
A healthy canine tear film has three layers:
- Lipid layer (outer): Produced by meibomian glands along the eyelid margins; prevents evaporation
- Aqueous layer (middle): Produced by lacrimal and nictitans glands; provides moisture, nutrients, and antibodies (IgA)
- Mucin layer (inner): Produced by conjunctival goblet cells; helps tears adhere to the corneal surface
When any layer is disrupted, the eye compensates. A deficient lipid layer leads to rapid evaporation, triggering reflex tearing — this is why dogs with meibomian gland dysfunction often have paradoxically watery eyes despite underlying dryness. According to the Merck Veterinary Manual, epiphora (excessive tear overflow) occurs when tear production exceeds drainage capacity or when the drainage system is obstructed.
The Nasolacrimal Drainage Pathway
Tears normally drain through two small openings called puncta — one on the upper eyelid and one on the lower — located near the inner corner of the eye. From there, tears flow through the nasolacrimal duct and empty into the nasal cavity. This is why dogs (and humans) get runny noses when they cry. When the puncta are absent, narrowed, or blocked, tears overflow onto the face instead. This condition, called punctal aplasia, is congenital in several breeds and is a leading cause of chronic watery eyes in young dogs.
Evolutionary Context: Why Dogs Developed This Tear System
The canine tear system evolved in ancestral canids as a protective mechanism for active, outdoor predators. Wolves and wild canids rely heavily on visual acuity for hunting across open terrain — dusty plains, brush, and snow all pose constant irritation risks to exposed corneas.
Robust tear production serves several evolutionary functions:
- Debris flushing: Rapid tear volume clears particulate matter encountered during high-speed pursuit through vegetation
- Corneal protection: The tear film's lysozyme and IgA antibodies fight bacterial exposure from prey contact and environmental pathogens
- UV and wind buffering: The lipid layer protects against desiccation in arid or windy environments where ancestral canids hunted
Research published in PLOS ONE (2018) found that domestic dogs produce a compound called N-(3-aminopropyl)-2-aminoethylphosphonate in their tears that may have antimicrobial properties not found in human tears — suggesting evolutionary adaptation to higher environmental pathogen exposure.
However, selective breeding for brachycephalic (flat-faced) skull shapes has disrupted the ancestral drainage architecture. When the muzzle shortened dramatically in breeds like Pugs and Shih Tzus, the nasolacrimal duct became compressed or kinked, and the shallow orbits left eyes more exposed — creating chronic tearing problems that would never have survived in a wild canid population.
Common Causes of Watery Eyes in Dogs
Understanding what to do if a dog has watery eyes starts with identifying the underlying cause. Here is a breakdown organized by category:
| Category | Specific Causes | Typical Signs | Urgency Level |
|---|---|---|---|
| Environmental Irritants | Dust, pollen, smoke, shampoo, wind exposure | Clear discharge, both eyes, temporary | Low — monitor 24 hrs |
| Allergies | Atopic dermatitis, food allergies, seasonal allergens | Clear tearing + itching, paw licking, ear infections | Moderate — schedule vet visit |
| Anatomical Issues | Punctal aplasia, entropion, ectropion, shallow orbits | Chronic tearing from puppyhood, tear staining | Moderate — breed-specific evaluation |
| Infections | Bacterial conjunctivitis, canine herpesvirus, distemper | Yellow/green discharge, redness, squinting | High — see vet within 24 hrs |
| Foreign Bodies | Grass awns, seeds, hair, debris under eyelid | One eye affected, pawing, acute onset | High — see vet same day |
| Corneal Damage | Ulcers, scratches, abrasions | Squinting, light sensitivity, cloudiness | Emergency — see vet immediately |
| Dry Eye (KCS) | Immune-mediated lacrimal gland destruction | Thick mucoid discharge, paradoxical tearing | High — requires lifelong treatment |
| Glaucoma | Increased intraocular pressure | Cloudy eye, enlarged eye, pain, vision loss | Emergency — risk of permanent blindness |
Breed Variations in Tear Production and Drainage
Genetics play a significant role in which dogs are prone to watery eyes. Brachycephalic breeds face the highest risk due to their compressed facial anatomy:
- Brachycephalic breeds (high risk): Shih Tzu, Pug, Pekingese, Bulldog, Boston Terrier, Lhasa Apso — shallow orbits, medial lower eyelid entropion, and kinked nasolacrimal ducts are common
- Breeds prone to punctal aplasia: Cocker Spaniel, Poodle, Golden Retriever, Miniature Schnauzer — congenital absence of tear drainage openings
- Breeds prone to KCS (dry eye): Cavalier King Charles Spaniel, English Bulldog, West Highland White Terrier, American Cocker Spaniel — immune-mediated lacrimal destruction
- Breeds with prominent tear staining: Maltese, Bichon Frise, Toy Poodle — porphyrin pigments in tears oxidize on light-colored fur, creating rust-colored streaks
According to the American Kennel Club, tear staining itself is cosmetic and not harmful, but the moisture that causes it can lead to secondary yeast or bacterial skin infections in the folds beneath the eye if not managed.
How Dogs Process Tears Differently Than Humans
A common misconception is that dogs cry emotional tears the way humans do. The science says otherwise.
| Myth | Scientific Fact |
|---|---|
| Dogs cry tears when they're sad | Dogs produce reflex tears (irritation) and basal tears (maintenance), but there is no peer-reviewed evidence that dogs produce emotional tears. A 2022 study in Current Biology suggested dogs may increase tear volume during joyful reunions with owners, but this remains preliminary and contested. |
| Watery eyes mean my dog is in pain | Not always. Clear tearing can be caused by harmless irritants. However, squinting combined with tearing is a reliable pain indicator. |
| Human eye drops are safe for dogs | Some are, many aren't. Visine (tetrahydrozoline) should never be used in dogs. Sterile saline eyewash is generally safe. Always consult your veterinarian before applying any medicated drops. |
| Tear staining means the eyes are infected | Tear staining is caused by porphyrins — iron-containing molecules naturally present in tears. It's a cosmetic issue, though the underlying moisture can predispose to skin infection. |
| If one eye is watery, both will follow | Unilateral tearing typically indicates a localized problem (foreign body, corneal ulcer, blocked duct on that side). Bilateral tearing more often points to systemic causes (allergies, environmental irritants, KCS). |
Physiological Mechanism: The Tearing Reflex Arc
When the cornea or conjunctiva detects an irritant, sensory nerve endings (primarily from the trigeminal nerve, cranial nerve V) send signals to the brainstem. The brainstem then triggers the lacrimal glands to increase aqueous tear production via parasympathetic fibers traveling through the facial nerve (cranial nerve VII). This reflex arc operates in milliseconds — faster than conscious processing — which is why your dog's eye may water before they even react behaviorally to a speck of dust.
The tear volume in a normal dog is measured using the Schirmer Tear Test (STT), where a standardized strip of filter paper is placed in the lower conjunctival sac for 60 seconds. Normal values are 15–25 mm of wetting. Values below 10 mm/min suggest keratoconjunctivitis sicca (KCS, or dry eye), while values above 25 mm/min may indicate reflex tearing from irritation or early-stage KCS where the gland is being overstimulated before failing.
Practical Steps: What to Do at Home
Step-by-Step Home Assessment
- Restrain gently: Have a second person hold your dog, or secure them in a sit/stay position. Approach from the side, not head-on, to reduce anxiety.
- Examine in good light: Use a phone flashlight held at an angle. Look for: foreign material, redness of the conjunctiva (the pink tissue around the eye), cloudiness of the cornea, squinting, or asymmetry between the two eyes.
- Flush with sterile saline: Use a sterile saline eyewash (available at pharmacies for $3–$6, brands like Steri-Unit or generic sterile saline). Apply 2–3 drops to the affected eye to flush out potential irritants. Never use contact lens solution — it contains preservatives that can damage the cornea.
- Wipe the periocular area: Use a clean, lint-free cloth dampened with warm water or a veterinary eye wipe (e.g., Vetericyn Eye Wipes, ~$12 for 30 count). Wipe from the inner corner outward, using a fresh section of cloth for each wipe.
- Monitor for 24 hours: If tearing resolves and the eye looks normal (clear cornea, white sclera, no squinting), the cause was likely a minor irritant. If symptoms persist or worsen, schedule a veterinary visit.
Managing Chronic Tear Staining
For dogs with persistent tear overflow that is anatomical rather than pathological:
- Daily wiping with a damp cloth prevents porphyrin buildup and secondary dermatitis
- Trimming hair around the inner eye corner reduces wicking (have a groomer or vet tech demonstrate safe technique with blunt-nosed scissors)
- Some owners report success with oral supplements containing Spirulina or probiotics to reduce porphyrin concentration, though peer-reviewed evidence is limited
- Avoid over-the-counter "tear stain removers" containing tylosin — this is an antibiotic, and prolonged use contributes to antimicrobial resistance
Estimated Veterinary Costs for Eye Evaluations
| Service | Typical Cost Range (2026) | What It Covers |
|---|---|---|
| Basic eye exam (general practice) | $65–$120 | Visual inspection, STT, fluorescein stain |
| Fluorescein stain | $25–$50 | Detects corneal ulcers/abrasions |
| Tonometry (glaucoma screening) | $30–$65 | Measures intraocular pressure |
| Specialist referral (veterinary ophthalmologist) | $200–$400 consultation | Advanced diagnostics, surgical evaluation |
| Nasolacrimal duct flush | $75–$200 | Clears blocked tear ducts under sedation |
| Entropion/ectropion surgery | $700–$2,500 per eye | Corrects eyelid rolling; breed-dependent complexity |
When Watery Eyes Signal a Serious Problem
🚨 Seek Veterinary Care Immediately If You Notice:
- Squinting or holding the eye closed — this almost always indicates corneal pain (ulcer, scratch, or foreign body)
- Cloudy or blue-tinged cornea — could indicate corneal edema, ulcer, or acute glaucoma
- Visible third eyelid protrusion — may signal pain, neurological issues, or "cherry eye" (prolapsed nictitans gland)
- Yellow, green, or bloody discharge — suggests infection or severe inflammation
- Eye appears enlarged or bulging — emergency: possible glaucoma (intraocular pressure >25 mmHg risks permanent optic nerve damage within hours)
- Sudden vision changes — bumping into objects, inability to track treats
- Both eyes affected simultaneously with systemic signs — lethargy, nasal discharge, coughing (possible distemper or canine infectious respiratory disease)
Always consult your veterinarian for persistent or concerning eye symptoms. Eye conditions can deteriorate rapidly — a corneal ulcer can deepen to a descemetocele (near-perforation) within 24–48 hours without treatment.
Common Misconceptions About Dog Eye Tearing
Several widely repeated beliefs about canine tear production don't hold up to scrutiny:
"My dog's eyes water because they're emotional." While dogs absolutely experience emotions, the lacrimal system responds to physical stimuli, not psychological ones. If your dog seems to "cry" during stressful events (vet visits, thunderstorms), the tearing is more likely caused by increased sympathetic nervous system activity affecting tear gland blood flow, or by wind/debris exposure during the event itself.
"I should put my dog's eye drops in whenever they look watery." Using leftover prescription drops — especially those containing corticosteroids like dexamethasone — on an undiagnosed eye can be catastrophic. If a corneal ulcer is present, steroids inhibit healing and can lead to corneal perforation within days. Always have a fluorescein stain performed before applying any steroid-containing medication.
"Tear staining means I'm feeding the wrong food." While some anecdotal reports link certain food dyes or mineral content to increased tear staining, controlled studies have not established a strong dietary connection. The primary drivers are anatomical (drainage issues) and genetic (porphyrin concentration in tears). Switching foods is unlikely to resolve staining if the underlying drainage problem persists.
Related Conditions and Cross-References
- Keratoconjunctivitis Sicca (KCS / Dry Eye): Paradoxically causes watery-looking eyes as the lacrimal gland fails and mucus accumulates — requires lifelong cyclosporine (Optimmune) or tacrolimus treatment
- Cherry Eye: Prolapse of the nictitans gland; common in Bulldogs, Beagles, Cocker Spaniels; surgical replacement (not removal) is the standard of care
- Entropion: Inward-rolling eyelid causing eyelashes to scrape the cornea; triggers reflex tearing; surgical correction typically performed after 6 months of age
- Distichiasis: Abnormal eyelashes growing from the meibomian gland openings; irritates the cornea and causes chronic tearing; seen in Shih Tzus, Lhasa Apsos, Dachshunds
- Canine Conjunctivitis: Inflammation of the conjunctival tissue; may be allergic, bacterial, viral, or immune-mediated; treatment depends on the underlying cause
Frequently Asked Questions
Why do dogs get watery eyes?
Dogs get watery eyes when tear production exceeds the drainage capacity of the nasolacrimal system. This can be triggered by irritants (dust, pollen), infections, anatomical abnormalities (blocked tear ducts, eyelid malformations), allergies, corneal injuries, or even dry eye disease (where poor-quality tears trigger reflex overproduction). The tearing reflex is mediated by the trigeminal nerve detecting irritation and signaling the lacrimal glands via the facial nerve.
Can dogs cry emotional tears?
Current veterinary science does not support the idea that dogs produce tears in response to emotions. Tears in dogs serve protective and lubricating functions. A 2022 study from Japan's Azabu University suggested elevated tear volume during owner reunions, possibly linked to oxytocin release, but the findings were based on a small sample (18 dogs) and remain debated in the veterinary community. The AVMA does not currently recognize emotional tearing as a validated canine behavior.
How do dogs process visual and tear signals differently from humans?
Dogs have a third eyelid (nictitating membrane) that humans lack, which provides additional corneal protection and houses a tear-producing gland responsible for up to 30–50% of aqueous tear volume. Dogs also have a higher density of rod photoreceptors (for low-light vision) and fewer cones (for color), meaning their visual processing prioritizes motion detection over detail. Their tear film is structurally similar to humans but may contain unique antimicrobial compounds adapted to their more environmentally exposed lifestyle.
What does it mean when my dog has one watery eye?
Unilateral (one-sided) tearing typically points to a localized problem on that side: a foreign body trapped under the eyelid, a corneal scratch or ulcer, a blocked nasolacrimal duct on that side, or an eyelid abnormality like entropion. It is less likely to be caused by systemic allergies or environmental irritants, which usually affect both eyes equally. A veterinary exam with fluorescein staining is the safest way to determine the cause.
Is it normal for my dog to have watery eyes every day?
For certain brachycephalic breeds (Pugs, Shih Tzus, Bulldogs), mild daily tear overflow is common due to their facial anatomy and is considered "normal for the breed" — though not ideal. For most other breeds, daily persistent tearing is not normal and warrants investigation. A Schirmer Tear Test and nasolacrimal duct evaluation can determine whether the cause is overproduction, under-drainage, or an underlying condition like early KCS.
Is watery eyes in dogs different from human watery eyes?
The basic mechanism is the same — reflex tearing in response to irritation or obstruction of drainage. However, dogs have the additional tear-producing nictitans gland and a third eyelid that humans lost during evolution. Dogs are also more prone to breed-specific anatomical issues (punctal aplasia, medial entropion) that have no direct human equivalent. Treatment differs too: many human OTC eye products (decongestant drops, antihistamine drops) are not safe for canine use.
References
- Merck Veterinary Manual — Epiphora in Small Animals
- AKC — Understanding Dog Eye Discharge
- AVMA — Dog Care Resources
- Kikusui et al. (2022) — Tears and oxytocin in domestic dogs, Current Biology
Beth Carrasco
All our authors care for dogs every day — read more of their work on the authors page.
