Excessive Tearing in Horses – Vet Guide 2025 🩺

By Dr Duncan Houston, BVSc

Introduction

When tears trail down your horse’s face, it’s not just a cosmetic issue—it's often a sign your horse may be in discomfort, or worse, jeopardizing its vision. In this 2025 guide, Dr Duncan Houston explains causes, diagnostics, treatments, and preventive strategies, offering horse owners clarity and confidence.

Why Early Veterinary Assessment is Crucial

• Eye tissue sensitivity: The eye's delicate structures can deteriorate rapidly—corneal ulcers can lead to blindness in hours without prompt treatment. 🕒
• Multiple underlying causes: From blocked tear ducts to infections or uveitis, tearing is a symptom—not the disease.
• Prognosis depends on timing: Early diagnosis greatly improves outcomes.

How Tears are Routed in the Horse Eye

Tears produced by the lacrimal glands are meant to flow through the nasal cavity via the nasolacrimal duct. Issues in this system can cause overflow (epiphora) on the face.

Primary Causes of Excessive Tearing

1. Blocked Tear Duct (Nasolacrimal Duct Occlusion)

This is one of the most common causes of chronic tearing.

Why It Happens

• ***Inflammation/debris*** from infections, sinus disease, or dental issues:contentReference[oaicite:2]{index=2}
• ***Mucoid plugs*** or dacryoliths can form in the duct:contentReference[oaicite:3]{index=3}
• ***Congenital narrowing or aplasia*** seen in some foals:contentReference[oaicite:4]{index=4}
• ***Trauma, tumors, or nearby inflammation*** can physically compress the duct:contentReference[oaicite:5]{index=5}

Signs to Spot

• Watery discharge streaming down cheek (clear to mucopus)
• Swollen eyelids or hair loss near tear-streak area:contentReference[oaicite:6]{index=6}
• Recurring cycles as ducts re-block after flushing

Diagnostic Steps

• Fluorescein dye test—dye should run from eye to nostril
• Vet flushes duct with sterile saline via nostril under sedation:contentReference[oaicite:7]{index=7}
• Further imaging (dacryocystorhinography or endoscopy) if flushing fails:contentReference[oaicite:8]{index=8}

Treatment Protocol

• Daily gentle cleansing and fly mask protection:contentReference[oaicite:9]{index=9}
• Regular vet flushes with saline, possibly with added antibiotic/steroid solution:contentReference[oaicite:10]{index=10}
• Antibiotic eye drops or ointment where infection is present
• Repeat flushing if blockage returns
• In refractory cases, surgical creation of new drainage canal (canaliculorhinostomy):contentReference[oaicite:11]{index=11}

2. Corneal Injuries & Ulcers

Traumas, foreign bodies, or environmental hazards can injure the cornea, causing immediate tearing and pain.

Causes

• Hay pokes, sharp grasses, dust, UV glare:contentReference[oaicite:12]{index=12}
• Conjunctivitis often accompanies minor debris irritation:contentReference[oaicite:13]{index=13}

Clinical Signs

• Cloudiness or opaque patches on cornea
• Pain behaviors—squinting, blinking, head shaking:contentReference[oaicite:14]{index=14}
• Thick or purulent discharge

Diagnosing Ulcers

• Fluorescein stain to reveal epithelial loss:contentReference[oaicite:15]{index=15}
• Slit-lamp examination for ulcer depth assessment:contentReference[oaicite:16]{index=16}
• Microbial culture if infection suspected:contentReference[oaicite:17]{index=17}

Treatment Plan

• Topical antibiotics (e.g., chloramphenicol, gentamicin) multiple times daily:contentReference[oaicite:18]{index=18}
• Atropine drops to relieve iris spasm and pain:contentReference[oaicite:19]{index=19}
• Systemic NSAIDs (flunixin) to manage pain/inflammation:contentReference[oaicite:20]{index=20}
• Anti-collagenase agents for melting ulcers (e.g. serum, EDTA, tetracycline):contentReference[oaicite:21]{index=21}
• Sub-palpebral lavage systems for meds in non-compliant horses:contentReference[oaicite:22]{index=22}
• Eye protection and box rest help prevent worsening
• Referral or surgery for deep or non-healing ulcers:contentReference[oaicite:23]{index=23}

3. Internal Eye Conditions: Uveitis, Glaucoma

Conditions like equine recurrent uveitis (ERU) and glaucoma cause internal inflammation—and often tearing.

Equine Recurrent Uveitis (ERU)

• Leading cause of equine blindness worldwide:contentReference[oaicite:24]{index=24}
• Signs: tearing, redness, squinting, cloudiness, small pupils:contentReference[oaicite:25]{index=25}
• May be autoimmune or infection-triggered (Leptospira, Streptococcus):contentReference[oaicite:26]{index=26}

Glaucoma"

Raised intraocular pressure leads to tearing, pain, corneal cloudiness, and vision loss.

Diagnosis & Treatment

• Ophthalmic evaluation including slit lamp and tonometry
• Topical/systemic anti-inflammatories and pressure reducers
• Referral to ophthalmologist for advanced therapies

4. Conjunctivitis & Allergies

Irritants or allergens can inflame the conjunctiva and provoke excess tearing.

• Signs include red, itchy eyes, mild tearing, and goopy discharge:contentReference[oaicite:27]{index=27}
• Allergens—dust, pollen, flies, mold induce tearing:contentReference[oaicite:28]{index=28}
• Treat with topical antihistamines, mast cell stabilizers, antibiotics or steroids
• Use environmental controls—fly masks, dust suppression:contentReference[oaicite:29]{index=29}
• Vet exam essential to rule out deeper pathology

5. Eye Membrane or Tumor Issues

Tearing can result from:

• Inflammation or tumors in eyelid membranes
• Squamous cell carcinoma near medial canthus:contentReference[oaicite:30]{index=30}

Diagnosis via exam, ultrasound, biopsy. Treatment varies from topical meds to surgery or cryotherapy:contentReference[oaicite:31]{index=31}.

Diagnostic Flowchart – Step by Step

1. Perform visual inspection and history review.
2. Conduct fluorescein dye test—if positive, investigate ulcers.
3. Check nasolacrimal patency—flush if blocked.
4. Assess internal eye and pressure for uveitis/glaucoma.
5. Use slit-lamp, tonometry, cytology, culture where needed.
6. Refer to ophthalmologist if deeper structures involved or treatment stalls.

Prevention & Routine Eye Care

• Daily eye checks—look for tearing, squinting, discharge.
• Flies/dust control—fly masks and clean environments.
• Adequate lighting to see subtle issues early.
• Prompt vet involvement at the first sign of care, not waiting for a crisis.

Conclusion

Excessive tearing is a symptom that shouldn’t be ignored. From simple duct blockages to sight-threatening uveitis or ulcers, early detection, appropriate diagnostics, and prompt veterinary care can save your horse’s vision and improve its quality of life.

Need Help Now?

Have concerns? Don’t wait—reach out to Ask A Vet via AskAVet.com or download our app for on-demand advice from qualified vets, including detailed image assessments. 🩺📱