Canine conjunctivitis (pink eye)

Symptoms an owner can spot at home

• Redness of the white of the eye or the inner eyelids
• Watery, mucoid, or yellow/green discharge
• Squinting or holding the eye partially closed
• Pawing at or rubbing the eye
• Swelling of the conjunctiva (chemosis)

When to see a vet

• Any eye that is squinting, painful, or has a change in appearance, corneal ulcers hide behind conjunctivitis and progress within hours
• Yellow or green discharge, fever, or lethargy
• Conjunctivitis in a dog with a known dry eye (KCS) diagnosis or previous corneal ulcer
• Both eyes affected in a dog with recent boarding or daycare exposure

What it is

Conjunctivitis in dogs is almost never a diagnosis on its own, it is a sign of something else. The most common primary causes are environmental allergies (atopic dermatitis often affects eyes and skin together), dry eye (keratoconjunctivitis sicca, KCS), eyelid conformation problems like entropion or ectropion, corneal ulceration, and infectious agents (bacteria, occasionally canine distemper virus, canine adenovirus).

Because the presentation is nonspecific and the differential includes vision-threatening conditions, self-treating with over-the-counter human eye drops is a common way to make a corneal ulcer worse, several human formulations are contraindicated in dogs.

How vets diagnose it

A minimum ophthalmic exam includes a Schirmer tear test (screen for dry eye), fluorescein staining (screen for corneal ulcer), intraocular pressure measurement (rule out glaucoma), and fundic examination. Cytology or culture is added when infection is suspected. Referral to a veterinary ophthalmologist is warranted for recurrent, non-responsive, or vision-threatening cases.

Treatment overview

This is editorial overview, not a treatment plan. Treatment always targets the underlying cause: topical cyclosporine class for KCS, corrective surgery for eyelid conformation, topical antibiotic class for bacterial infection, allergy management for atopic-driven cases. Steroid-class drops are only safe after fluorescein staining excludes a corneal ulcer, applying steroids to an ulcerated cornea can perforate the eye.

What owners can do

• Do not use human eye drops without a vet's direction.
• Wipe discharge away with a damp gauze pad; do not touch the eye surface.
• Manage underlying atopy aggressively, eye signs are often the first flare.
• For breeds prone to entropion or dry eye, book annual ophthalmic screening.