Conjunctivitis (Pink Eye) in Dogs: Causes, Treatment, and Home Care

Aug 29 • 10 min read

Your dog's eye looks pink and puffy this morning, and there's a bit of gunk stuck in the corner that wasn't there last night. He's blinking more than usual, maybe pawing at his face. Before you reach for anything in the medicine cabinet, it helps to know exactly what's going on.

Conjunctivitis, commonly called pink eye, is inflammation of the conjunctiva the thin, pink membrane lining your dog's eyelids and covering the white of the eye. It's one of the most common eye problems in dogs, with causes ranging from a foreign speck of dust to bacterial or viral infection to allergies. Signs include redness, swelling, discharge, and mild discomfort, and while some cases clear up with simple care, others need a vet's diagnosis to find out exactly what's driving it.

Key Takeaways

Conjunctivitis is inflammation of the conjunctiva, the thin membrane lining the eyelids and covering the white of the eye it's very common in dogs.
Signs include redness, swelling around the cornea, eye discharge, and mild discomfort or squinting.
Conjunctivitis in only one eye often points to a foreign object, a tear duct problem, or dry eye, while both eyes affected usually means infection or environmental irritants.
The appearance of the eye alone usually isn't enough for a vet to pinpoint the cause diagnosis often needs a history, exam, conjunctival scrapings, and a tear test.
Because conjunctivitis has so many possible causes, treatment is rarely one-size-fits-all, and your vet may combine several approaches.
A red, uncomfortable eye should never be treated as "wait and see," since some look-alike conditions can threaten your dog's vision if left untreated.

What Is Conjunctivitis (Pink Eye) in Dogs?

Side-by-side illustration comparing a healthy dog eye to one with conjunctivitis.

The conjunctiva is a thin membrane that lines the inside of your dog's eyelids and extends over the white of the eye, according to the Merck Veterinary Manual. It plays a real functional role helping create tears, protecting the eye from foreign invaders, supporting normal eye movement, and aiding corneal healing after injury. Conjunctivitis, also called pink eye, is inflammation of this membrane, and Merck notes it's common in dogs.

Merck describes the classic signs plainly: redness of the eye, swelling of the tissue around the cornea, discharge from the eye, and mild eye discomfort. VCA Hospitals adds a bit more visual detail in a healthy dog, the conjunctiva of the eyelids isn't very visible and has a pale pink colour. With conjunctivitis, that membrane turns red and swollen, and discharge can appear cloudy, yellow, or greenish.

It's important to identify and treat conjunctival problems promptly, because Merck notes some can point to a more generalised disease elsewhere in the body, or lead to vision loss if left untreated. Conjunctivitis on its own is usually manageable, but the underlying cause is what really determines the outlook.

What Causes Conjunctivitis in Dogs?

Conjunctivitis has a genuinely long list of possible causes, and Merck notes the appearance of the conjunctiva alone usually isn't enough for a vet to pin down which one is at play. Common triggers include:

Infections viral or bacterial infections are common causes, especially when both eyes are affected.
Environmental irritants and allergens dust, smoke, chemical fumes, and pollen can all trigger inflammation.
Foreign objects a speck of dirt, a grass seed, or debris trapped under the eyelid.
Tear film problems both dry eye (not enough tears) and tear duct blockages (poor drainage) can lead to secondary conjunctivitis.
Eyelid and eyelash abnormalities conditions like entropion (eyelid rolling inward) or abnormal eyelash growth cause ongoing irritation as hair rubs against the eye.
Parasites VCA Hospitals notes that parasites can also be an underlying cause in some cases.
Other eye conditions corneal ulcers, anterior uveitis (inflammation inside the eye), and glaucoma can all present with a red, inflamed-looking eye that resembles simple conjunctivitis.
Trauma any injury to the eye or surrounding area.

Because so many different problems can produce the same basic symptoms, Merck notes that a mucus-and-pus discharge might prompt your vet to prescribe a topical antibiotic — but the antibiotic alone may not resolve things if another factor, like a foreign object or an eyelid abnormality, is also contributing. Your vet will typically check for all of these possibilities rather than treating the redness in isolation.

One Eye vs Both Eyes: A Useful Clue

Infographic showing likely causes of dog conjunctivitis based on whether one or both eyes are affected.

One detail that genuinely helps narrow things down is whether one or both eyes are affected. According to Merck, conjunctivitis in only one eye may result from a foreign object, inflammation of the tear sac, or dry eye. Conjunctivitis occurring in both eyes, on the other hand, is commonly caused by viral or bacterial infection, with environmental irritants and allergens being other common culprits.

This isn't a hard-and-fast rule your vet will use in isolation, but it's a genuinely useful piece of information to mention at your appointment. If your dog's left eye is red and goopy while the right eye looks completely normal, that detail alone helps your vet prioritise which causes to investigate first.

How Vets Diagnose Conjunctivitis in Dogs

Because conjunctivitis can stem from so many different root causes, Merck is direct that a physical exam alone usually isn't enough for a specific diagnosis. A complete workup often involves:

A detailed medical history
A full physical exam
Tests on conjunctival scrapings (examining cells collected from the surface of the eye)
A Schirmer tear test, which measures tear production
Occasionally, a biopsy in more complex or non-responsive cases

Your vet will also specifically check for foreign objects, environmental irritants, parasites, and defects in eyelid shape or form all of which can contribute to or mimic conjunctivitis. VCA Hospitals frames the main diagnostic goal simply: figuring out whether the conjunctivitis is a primary problem on its own, or secondary to something else going on in or around the eye.

Treatment: Why There's No One-Size-Fits-All Answer

Because conjunctivitis can have multiple causes acting together, Merck notes your vet may prescribe a combination of treatments rather than a single fix. What that combination looks like depends entirely on what's driving the inflammation:

Bacterial infection typically calls for a topical antibiotic, applied as drops or ointment.
Viral infection is usually managed with supportive care and sometimes steroid drops, since antibiotics don't treat viruses.
Allergic causes may need antihistamines, anti-inflammatory drops, or in some cases, addressing the allergy itself.
Foreign objects need to be located and removed before the eye can heal properly.
Underlying dry eye (KCS) requires medications like cyclosporine or tacrolimus to stimulate tear production, alongside lubricants — VCA Hospitals notes this is a different treatment path entirely from a simple infection.
Eyelid or eyelash abnormalities often need surgical correction, since medication alone won't stop the ongoing irritation from hair rubbing against the eye.

VCA Hospitals notes that most cases of conjunctivitis have a very good prognosis, especially once the underlying cause is identified and addressed. Severe, chronic, or recurrent conjunctivitis carries a more guarded outlook, and conditions like dry eye or immune-mediated disorders may need lifelong management rather than a short course of drops.

Home Care for a Dog with Conjunctivitis

Once your vet has examined your dog's eye and ruled out anything urgent, a few simple habits support recovery and comfort:

Give any prescribed drops or ointment exactly as directed, for the full course, even if the eye looks better after a couple of days.
Gently wipe away discharge with a clean, damp cloth before applying medication, so the drops can actually reach the eye's surface.
Keep long facial fur trimmed away from the eyes if your breed tends to grow hair that can rub against the cornea.
Avoid known environmental triggers where possible — smoke, strong household chemical fumes, and heavy dust exposure can all aggravate a healing eye.
Never use leftover human eye drops or medication prescribed for a previous condition without checking with your vet first, since the wrong drop can actively worsen certain underlying causes, such as a corneal ulcer.
Book a follow-up if the eye isn't visibly improving within a few days of starting treatment, or if it seems to be getting worse.

When Pink Eye Is Actually an Emergency

Most conjunctivitis is uncomfortable rather than dangerous, but a handful of warning signs mean it's time to skip the wait-and-see approach entirely. Book a same-day vet visit if you notice:

Sudden, severe redness in just one eye
Obvious pain heavy squinting, holding the eye shut, or pawing repeatedly at the face
Cloudiness or a visible change in the colour of the eye
Thick, coloured discharge that keeps returning even after cleaning
Any sign your dog's vision seems affected, such as bumping into furniture

These signs can point to conditions like a corneal ulcer, anterior uveitis, or glaucoma all of which can resemble simple conjunctivitis at first glance but carry a real risk to your dog's vision if treatment is delayed.

FAQ

Is dog conjunctivitis contagious to other pets?
It depends entirely on the cause. Viral or bacterial conjunctivitis can potentially spread between dogs in close contact, while conjunctivitis caused by allergies, a foreign object, or an eyelid abnormality is not contagious at all. Your vet's diagnosis will clarify which situation you're dealing with.

Can I just clean my dog's eye at home instead of seeing a vet?
Gentle cleaning with a damp cloth can help remove discharge, but it won't resolve the underlying cause. Because conjunctivitis has so many possible triggers some of which need prescription treatment or even surgery a vet visit is the safest first step rather than managing it at home alone.

Why does my dog only have redness in one eye?
One-sided conjunctivitis often points to a localised cause like a foreign object, a tear duct problem, or dry eye in that specific eye. This is a useful detail to share with your vet, since it can help narrow down the likely cause compared to both eyes being affected at once.

How long does conjunctivitis in dogs usually last?
With the right treatment for the underlying cause, many straightforward cases improve within several days to two weeks. Chronic or recurrent conjunctivitis, especially when linked to allergies, dry eye, or an eyelid abnormality, may need ongoing management rather than a single course of treatment.

Should I be worried if my dog's pink eye doesn't improve with antibiotic drops?
Yes, this is worth a prompt follow-up. If antibiotics alone aren't helping, it often means another factor such as a foreign object, an eyelid abnormality, allergies, or a completely different eye condition is also involved and needs to be addressed directly.