Eye inflammation (conjunctivitis) in the dog

What is conjunctivitis in the dog?

Conjunctivitis is an inflammation of the conjunctiva — the mucous membrane that covers the inside of the eyelids and the white of the eye. In dogs, primary bacterial conjunctivitis is rare; most cases are secondary to an underlying cause [4]. Complaints such as redness, discharge, blinking and rubbing at the eye are the result of that underlying condition, not of a standalone infection.

Most common underlying causes

Diagnosis: more than a look in the eye

A proper diagnosis requires a complete ophthalmic examination. The Schirmer tear test (STT1) is indispensable to detect KCS — a result below 15 mm/min indicates insufficient tear production [3]. Additionally, fluorescein staining of the cornea (to detect ulcers) and tonometry (to rule out glaucoma) are a standard part of the consultation [4]. Without this examination there is a risk that the wrong treatment is given — sometimes with serious consequences for vision.

Treatment: cause-oriented

• KCS is treated with topical ciclosporin A or tacrolimus, which inhibit the immune-mediated gland destruction. This is a lifelong treatment [3].
• Bacterial infection justifies topical antibiotics, but only upon proven bacterial involvement [4].
• Corticosteroids may only be used after corneal ulcers have been ruled out — use in the presence of an ulcer can lead to perforation [4].
• Viral conjunctivitis (CHV-1, CAV-2) can be treated with antiviral eye drops (idoxuridine, trifluridine) [1].
• Anatomical causes often require surgical correction.

Supplementary and natural options: an honest picture

For supplementary agents such as chamomile rinses, colloidal silver, honey eye drops or herbal preparations there is no clinical evidence of effectiveness in dogs with conjunctivitis. Some agents can irritate the eye or — in the presence of an underlying ulcer — cause active damage. Rinsing the eye with physiological saline (0.9% NaCl) can provide temporary relief in mild eye irritation due to dust or pollen, but does not resolve the underlying cause.

Supplementary ≠ replacement. Without diagnosis and treatment of the underlying cause, conjunctivitis will recur or worsen in almost all dogs [3][4]. Delaying veterinary care in the presence of signs of severe inflammation or ulceration increases the risk of permanent damage.

When to go to the vet?

Veterinary evaluation is indicated for any conjunctivitis that persists longer than 24–48 hours, recurs or is accompanied by pain, photophobia or change of the eye. In the case of the red flags below, immediately.