Tear Marks in Dogs: The Science Behind Epiphora and Stained Fur
Why do tear marks form on dogs? Explore the science of epiphora, porphyrin staining, breed predispositions, and evidence-based prevention strategies.
What Are Tear Marks in Dogs? The Quick Answer
If you share your home with a Bichon Frise, Maltese, Shih Tzu, or any brachycephalic (short-faced) breed, you've likely waged a quiet war against those rust-colored streaks beneath your dog's eyes. Tear marks — sometimes called tear stains — affect an estimated 20-25% of small and toy breed dogs, according to veterinary dermatology surveys, though they can appear in any breed with certain anatomical features.
Understanding tear marks requires looking past the cosmetic frustration and into the actual physiology of canine tear production, drainage, and the chemistry of porphyrin oxidation. This isn't just about keeping your dog's face clean — it's about recognizing when excessive tearing is normal anatomy and when it signals something your veterinarian needs to address.
The Science of Porphyrins: Why Dog Tears Stain Fur
How Porphyrins Work at the Molecular Level
Porphyrins are a class of organic compounds that serve as the building blocks for critical molecules like hemoglobin (the oxygen-carrying protein in red blood cells), myoglobin, and certain enzymes. The canine body produces porphyrins as a natural byproduct of red blood cell breakdown — specifically, when heme groups are metabolized.
In dogs, porphyrins are excreted through multiple pathways: bile, urine, saliva, and tears. The tears that overflow onto the face contain these porphyrin molecules, which are initially colorless. However, when exposed to oxygen and ultraviolet light, porphyrins undergo oxidation, turning from clear to pink, then to reddish-brown over 24-48 hours.
This is why fresh tear marks often appear pinkish, while chronic, untreated stains develop a deep rust or chocolate-brown color. The oxidation process is similar to how a sliced apple turns brown when exposed to air — it's a surface-level chemical reaction accelerated by light, moisture, and bacterial activity on the fur.
A 2018 study published in the Journal of Veterinary Dermatology confirmed that porphyrin concentration in canine tears varies significantly between individual dogs, which explains why some dogs develop heavy staining while others of the same breed show minimal marks despite similar tear volumes.
The key takeaway: porphyrins are not a sign of disease in themselves. They are normal metabolic byproducts. The problem arises when tears — which contain porphyrins — fail to drain properly through the nasolacrimal system and instead pool on the fur where oxidation occurs.
Canine Tear Anatomy: How Dogs Produce and Drain Tears
To understand why tear marks form, you need to understand the canine lacrimal (tear) system, which operates differently from the human system in several important ways.
Tear production happens in two main glands: the lacrimal gland (located above the outer corner of the eye) and the nictitans gland (associated with the third eyelid, or nictitating membrane). Together, these glands produce the aqueous (watery) layer of the tear film. Additional lipid and mucin layers come from the meibomian glands along the eyelid margins and conjunctival goblet cells, respectively.
Tear drainage follows a specific pathway:
- Tears spread across the eye surface with each blink
- Tears collect at the medial canthus (inner corner of the eye) in a small pool called the lacrimal lake
- Tears enter the superior and inferior puncta — two tiny openings on the inner eyelid margins
- Tears flow through the canaliculi (small channels) into the lacrimal sac
- Tears drain through the nasolacrimal duct into the nasal cavity
In a dog with a properly functioning system, tears never overflow onto the face. They drain internally, which is why you don't normally see wetness below a dog's eyes. Epiphora occurs when this drainage pathway is disrupted at any point — from the puncta to the nasal cavity.
Evolutionary Context: Why Dogs Have This System
The nasolacrimal drainage system is conserved across most mammalian species, inherited from early mammalian ancestors. In wolves and wild canids, efficient tear drainage serves a functional purpose: maintaining clear vision during hunting and territorial patrols without moisture obscuring the visual field. Wild canids rarely show tear staining because natural selection favors individuals with patent (open) drainage systems — impaired vision from chronic epiphora would reduce hunting success.
In domestic dogs, particularly brachycephalic breeds developed over the last 200-300 years through intense selective breeding for flat faces, the skull compression that creates the desired "baby-faced" appearance simultaneously distorts the nasolacrimal duct pathway. The duct becomes kinked, compressed, or misaligned, creating a drainage bottleneck that would be selected against in wild populations. This is a classic example of how artificial selection for cosmetic traits can produce functional trade-offs.
Why Do Dogs Get Tear Marks? The Primary Causes
Epiphora — and the resulting tear marks — can stem from several distinct mechanisms. Identifying which one affects your dog determines both the treatment approach and whether veterinary intervention is needed.
| Cause | Mechanism | Breeds Most Affected | Vet Visit Needed? |
|---|---|---|---|
| Punctal aplasia | Missing or underdeveloped tear drainage openings (puncta) | Cocker Spaniels, Poodles, Bichon Frises | Yes — may require surgical correction |
| Brachycephalic anatomy | Shallow orbits and compressed nasolacrimal ducts prevent normal drainage | Shih Tzus, Pugs, Pekingese, Bulldogs | Yes — monitor for secondary infections |
| Entropion/Ectropion | Eyelids roll inward (entropion) or outward (ectropion), disrupting tear flow | Shar-Peis, Bulldogs, Bloodhounds, Basset Hounds | Yes — surgical correction often needed |
| Distichiasis/Trichiasis | Aberrant eyelashes or facial hair rubs against the cornea, stimulating excess tear production | Shih Tzus, Lhasa Apsos, Poodles | Yes — hair removal or surgery |
| Conjunctivitis/Keratitis | Inflammation of the conjunctiva or cornea triggers reflex tearing | Any breed | Yes — requires medical treatment |
| Nasolacrimal duct obstruction | Blockage anywhere along the drainage pathway from debris, infection, or congenital narrowing | Small breeds, brachycephalic breeds | Yes — flushing or surgical intervention |
| Hair wicking | Long facial hair acts as a wick, drawing tears from the eye surface onto the fur | Maltese, Yorkshire Terriers, Havanese | Usually no — grooming management |
How Is This Different from Humans?
Humans also produce porphyrins in their tears, but human tear staining is virtually nonexistent for two reasons. First, human tears drain more efficiently due to the anatomical structure of our orbits and nasolacrimal ducts. Second, human tears contain lower concentrations of porphyrins relative to dogs. Additionally, humans don't have fur around the eyes to trap and hold tears in place for oxidation. When humans do experience excessive tearing (epiphora), the tears typically run down the cheek and evaporate or are wiped away before staining can occur.
Breed Variations: Which Dogs Are Most Prone to Tear Marks?
Tear marks are not evenly distributed across dog breeds. The predisposition maps closely to skull shape, eye prominence, and facial hair characteristics.
High-risk breeds (tear marks affect an estimated 40-60% of individuals):
- Maltese — Long facial hair combined with relatively prominent eyes creates both wicking and overflow conditions
- Bichon Frise — Dense facial coat and slightly brachycephalic structure
- Shih Tzu — Brachycephalic anatomy with large, prominent eyes and long facial hair
- Poodle (Toy and Miniature) — Higher rates of punctal aplasia and hair growth around the eyes
- Pug — Extreme brachycephalic structure with shallow orbits; tears frequently overflow
- Pekingese — Flat face with prominent eyes and heavy facial coat
Moderate-risk breeds (15-30% of individuals affected):
- Havanese — Long facial hair with moderate eye prominence
- Lhasa Apso — Heavy facial hair and slightly brachycephalic features
- Yorkshire Terrier — Facial hair wicking, though less brachycephalic than other small breeds
- Cavalier King Charles Spaniel — Moderate brachycephalic features with large eyes
Low-risk breeds: Most dolichocephalic (long-faced) breeds like Greyhounds, Collies, and German Shepherds rarely develop tear marks because their nasolacrimal ducts follow a straight, unobstructed path and their eyes sit deeper within protective orbits.
When Tear Marks Signal a Problem: Medical Red Flags
When to See Your Veterinarian About Tear Marks
While chronic mild tear staining is often a cosmetic issue, the following signs warrant prompt veterinary evaluation:
- Sudden onset of heavy tearing in a dog that previously had clean fur
- Squinting, blinking excessively, or pawing at the eye — signs of corneal pain or ulceration
- Yellow or green discharge — indicates bacterial infection, not just tears
- Redness or swelling of the conjunctiva (the pink tissue around the eye)
- Cloudiness or color change in the eye itself
- Asymmetric tearing — one eye producing significantly more tears than the other
- Skin irritation or hair loss on the face below the eyes from chronic moisture
- Foul odor from the stained area — suggests secondary bacterial or yeast (Malassezia) infection
Always consult your veterinarian before starting any treatment for tear marks, especially if your dog shows any of the above symptoms. Eye conditions can deteriorate rapidly, and delayed treatment of corneal ulcers can lead to permanent vision loss within 24-48 hours.
Your veterinarian will typically perform a thorough ophthalmic exam that may include a Schirmer tear test (measuring tear production volume), fluorescein staining (checking for corneal ulcers), a nasolacrimal flush test (verifying duct patency), and examination of the eyelids and eyelashes under magnification. Expect to pay $80-$200 for a standard ophthalmic exam, with additional diagnostics adding $50-$150 depending on the tests required.
Myth vs. Fact: Common Misconceptions About Tear Marks
| Myth | Fact |
|---|---|
| "Tear marks mean my dog is sad or crying emotionally." | False. Dogs do not produce emotional tears. Research published in Current Biology (2022) showed that dogs may increase tear volume when reuniting with owners, but this is linked to oxytocin release, not emotional "crying" as humans experience it. Chronic tear marks are anatomical, not emotional. |
| "Changing my dog's food will eliminate tear stains." | Mostly false. While food allergies can cause facial itching that leads to increased face-rubbing and secondary staining, there is no peer-reviewed evidence that specific diets reduce porphyrin levels in tears. The claim that grain-free or "premium" diets eliminate tear stains is not supported by veterinary research. |
| "Apple cider vinegar in water cures tear stains." | Unproven and potentially risky. While ACV may alter systemic pH slightly, there is no evidence it reduces tear porphyrin levels. Adding ACV to drinking water can also discourage water intake, leading to dehydration — especially dangerous in small breeds. |
| "Tear stain removers with antibiotics are the most effective solution." | Caution required. Some over-the-counter tear stain products previously contained tylosin or metronidazole (antibiotics) without labeling. The FDA has warned against undisclosed antibiotic use in pet products. Long-term low-dose antibiotic exposure contributes to antimicrobial resistance. Use only veterinary-prescribed products. |
| "Tear marks are just cosmetic and never harmful." | Partially false. While the stains themselves are cosmetic, the chronically moist fur creates an environment for bacterial and yeast overgrowth. Untreated, this can lead to facial dermatitis, skin ulceration, and secondary infections that require medical treatment. |
| "All white dogs get tear stains." | False. Tear marks are most visible on white and light-colored fur, but they can occur on any coat color — they're simply harder to see on dark fur. The underlying epiphora can affect any breed with the right anatomical predisposition regardless of coat color. |
Practical Tear Mark Management: What Actually Works
Evidence-Based Tear Mark Prevention Protocol
Based on veterinary dermatology recommendations, here is a practical daily and weekly routine for managing tear marks:
Daily (2-3 minutes):
- Wipe the area below each eye with a soft, lint-free cloth dampened with warm water or a veterinary-recommended eye wipe (e.g., Eye Envy Tear Stain Remover or Angel Eyes Plus Wipes, approximately $12-$18 per container)
- Gently dry the area — moisture left on the fur accelerates porphyrin oxidation
- Check for any discharge color changes (clear = normal; yellow/green = vet visit)
Weekly (10-15 minutes):
- Trim facial hair around the inner eye corners to a length of approximately 3-5 mm using blunt-nosed grooming scissors — this eliminates the "wicking" effect
- Apply a thin layer of petroleum jelly or a veterinary-safe barrier ointment (e.g., Puralube Vet Ointment, ~$8-$12) to the fur below the eyes to create a moisture barrier
- Wash cloth bedding and any fabric your dog rests their face on
Monthly:
- Inspect tear drainage by gently pressing the area near the inner eye corner — if you see moisture emerge from the nostril on the same side, the nasolacrimal duct is patent
- Assess whether staining is increasing, stable, or decreasing to identify trends that may need veterinary attention
Products to Use and Products to Avoid
Generally safe options:
- Sterile saline eye wash (available at any pharmacy, $3-$6) for flushing debris
- Veterinary-formulated eye wipes without alcohol or hydrogen peroxide
- Blunt-nosed grooming scissors for facial hair trimming ($8-$15)
- Boric acid-based stain removers formulated specifically for canine use — boric acid has mild antibacterial properties and helps break down oxidized porphyrins on the fur surface
Products and practices to avoid:
- Hydrogen peroxide near the eyes — can cause corneal damage if it contacts the eye surface
- Human makeup remover or facial cleansers — pH and ingredient formulations are not designed for canine skin
- Products containing undisclosed antibiotics (check ingredient labels carefully)
- "Natural" remedies involving essential oils near the eyes — many essential oils are irritating or toxic to canine corneas
- Physical scrubbing or aggressive rubbing — damages hair follicles and can cause skin microabrasions that invite infection
Related Conditions and Cross-References
Tear marks don't exist in isolation. They connect to several other canine health and care topics that responsible owners should understand:
- Brachycephalic Obstructive Airway Syndrome (BOAS) — Breeds prone to tear marks due to flat faces often simultaneously suffer from BOAS. The same skull compression that kinks the nasolacrimal duct also narrows the nares and elongates the soft palate. If your brachycephalic dog has severe tear marks, discuss a BOAS evaluation with your vet.
- Facial fold pyoderma — The moist environment below the eyes often extends into facial skin folds (especially in Pugs, Bulldogs, and Pekingese), creating bacterial skin infections that require topical or systemic antibiotics.
- Dry eye (keratoconjunctivitis sicca or KCS) — Paradoxically, some dogs with dry eye develop tear-stained fur because the poor-quality tears they do produce are thick, mucoid, and don't drain properly. If your dog has both crusty eye discharge and staining, KCS should be ruled out with a Schirmer tear test.
- Corneal ulcers — Breeds with prominent eyes and tear staining are at higher risk for corneal injuries because the eyes are more exposed. Any sudden increase in tearing with squinting requires immediate veterinary attention.
Frequently Asked Questions About Tear Marks in Dogs
Why do dogs get tear marks?
Dogs get tear marks when tears overflow onto the face instead of draining through the nasolacrimal duct into the nose. The tears contain porphyrins — iron-containing molecules that oxidize when exposed to air and light, producing reddish-brown stains on the fur. The overflow can result from anatomical blockages, excessive tear production, or facial hair that wicks tears away from the eye surface.
Can dogs cry emotional tears?
Current scientific evidence suggests dogs do not produce tears in response to emotions the way humans do. A 2022 study in Current Biology found that dogs showed increased tear volume when reuniting with their owners, potentially linked to oxytocin release. However, this is a physiological response to social reunion, not emotional crying in the human sense. Chronic tear marks are not a sign that your dog is sad.
How do dogs process tear drainage differently from humans?
Both dogs and humans drain tears through a nasolacrimal system, but dogs have a longer, more tortuous nasolacrimal duct that passes through a more complex facial bone structure. In brachycephalic breeds, selective breeding has compressed this pathway. Humans also lack the facial fur that traps tears and allows porphyrin oxidation to occur visibly.
What does it mean when my dog suddenly has more tear marks than usual?
A sudden increase in tear marks usually means an increase in tear production or a new obstruction in the drainage pathway. Possible causes include conjunctivitis, a corneal scratch or ulcer, an eyelash growing into the eye (distichiasis), a foreign body under the eyelid, or a dental abscess that is compressing the nasolacrimal duct from below. A sudden change warrants a veterinary ophthalmic exam within 24-48 hours.
Is it normal for my dog to have tear marks?
For certain breeds — particularly brachycephalic breeds and small breeds with long facial hair — mild, chronic tear staining is common and often considered a normal consequence of their anatomy. However, "common" doesn't mean "ignore it." Even anatomically normal tear overflow requires daily cleaning to prevent secondary skin infections, and any change in the pattern or severity of staining should be evaluated by a veterinarian.
How do I remove existing tear stains from my dog's fur?
Existing oxidized stains cannot be "dissolved" — the porphyrin has permanently colored the hair shaft. Your options are: (1) carefully trim away the stained fur with blunt-nosed scissors and allow new, clean fur to grow in while maintaining a daily wiping routine, or (2) use a veterinary-safe stain-lightening product containing boric acid or mild enzymes to gradually lighten the stain over 2-3 weeks of consistent application. Never use bleach, hydrogen peroxide, or human hair-lightening products near your dog's eyes.
Are tear stain supplements worth trying?
Oral tear stain supplements typically contain ingredients like probiotics, cranberry extract, or marshmallow root. While generally safe, there is limited peer-reviewed evidence that they reduce porphyrin levels in tears. Some owners report improvement, which may be related to overall gut health changes affecting systemic inflammation. If you choose to try a supplement, select one with a National Animal Supplement Council (NASC) quality seal and discuss it with your veterinarian first. Expect to pay $15-$30 for a 60-day supply.
References
- Nagae, M. et al. (2022). "Dog tears and the reunion effect." Current Biology, 32(16). Available via Cell Press.
- Merck Veterinary Manual — Epiphora in Small Animals
- American Kennel Club — Tear Stains in Dogs: Causes and Treatment
- American College of Veterinary Ophthalmologists (ACVO) — Breed predispositions for nasolacrimal disorders
Beth Carrasco
All our authors care for dogs every day — read more of their work on the authors page.
