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

Signs to watch for

Conjunctivitis can affect one eye or both. Common signs include the following.

• Red or pink eyes, or a red, puffy lining inside the eyelids
• Swelling of the tissue around the eye
• Discharge that may be clear and watery, or thick, cloudy, yellow or green
• Blinking more than usual, or squinting
• Rubbing the face on the floor or furniture, or pawing at the eye

Some dogs also sneeze, have a runny nose or cough, which can point to an infection that affects more than the eyes. The pattern also gives your vet a clue. Trouble in only one eye raises the chance of something local, such as a foreign body or a blocked tear duct. When both eyes are affected, allergies, irritants, dry eye and infections are more likely.

Common causes

In dogs, conjunctivitis is very often a reaction to another problem rather than an infection that starts in the eye. Unlike in people and cats, bacteria are rarely the original cause. When bacteria are involved, they usually take advantage of something else, such as dry eye or an eyelash rubbing on the eye. That is why antibiotic drops on their own often do not fix the problem. Common causes include the following.

• Allergies. Dogs with atopic dermatitis, the itchy skin allergy, get conjunctivitis much more often than dogs with healthy skin. Dust, grasses and pollen are common triggers.
• Irritants, such as smoke, dust, sand, sprays and harsh chemicals
• Dry eye, or keratoconjunctivitis sicca, where the eye does not make enough tears
• Something stuck in the eye, such as a grass seed or plant material, which can hide behind the third eyelid
• Eyelid and eyelash problems, such as eyelids that roll inward or droop outward, or extra eyelashes that rub the eye
• A blocked tear duct
• Viral infections, such as canine distemper and canine herpesvirus
• Immune-related conditions, such as plasma cell conjunctivitis, seen most often in German shepherds
• Growths on the eyelids or the conjunctiva

Young dogs of large breeds sometimes develop follicular conjunctivitis. Small bumps form on the inner surface of the eyelids and on the third eyelid, usually as a reaction to allergens such as dust, grass and weeds. Dogs with droopy lids or deep-set eyes are more prone, because more debris collects in the eye. Many dogs outgrow it by about two years of age, although flare-ups can return. Eyelid shape problems are covered in our guide to entropion and ectropion, and skin and eye allergies in allergies in dogs and cats.

Problems that look like pink eye

A red eye is not always simple conjunctivitis. Several more serious problems inflame the conjunctiva too, and they need very different treatment.

• A corneal ulcer, a scratch or erosion on the clear front of the eye. It is very painful and can become serious quickly.
• Glaucoma, raised pressure inside the eye. The eye may look cloudy, bluish or enlarged.
• Uveitis, which is inflammation inside the eyeball
• Lens luxation, where the lens slips out of its normal position

This is why your vet checks the whole eye rather than just the redness. For more on two of the most urgent problems, see our guides to corneal ulcers and glaucoma in dogs.

When to see a vet

Eye problems are worth a vet visit even when they look minor, because untreated conjunctivitis and the conditions that mimic it can lead to serious damage or even loss of an eye. Contact your vet the same day, or an emergency clinic out of hours, if you notice any of these signs.

• Squinting, holding the eye shut, or obvious pain
• A cloudy, bluish or hazy eye
• One eye that looks bigger than the other, bulges or seems sunken
• Bleeding, a visible wound, or something stuck in the eye
• Chemicals, cleaning products or shampoo splashed into the eye
• Sudden changes in vision, such as bumping into furniture
• Eye discharge together with fever, coughing, a runny nose, poor appetite or tiredness, especially in a puppy or an unvaccinated dog

That last combination can be a sign of distemper, a serious viral disease. You can read more in our guide to canine distemper. Even mild redness or discharge deserves a call to your vet. If your dog has repeated episodes, your vet will want to look for the underlying cause.

Why human eye drops are risky

It is safer not to use drops from your own bathroom cabinet.

Redness-relief drops, such as Visine, contain decongestants that narrow the blood vessels in the eye. They are not approved for pets, they do nothing about the cause, and they can make conjunctivitis, glaucoma, allergic reactions and foreign bodies worse. If a dog chews the bottle and swallows the liquid, even a small amount can cause serious poisoning. Signs can start within half an hour and include vomiting, tiredness, agitation, wobbliness and a dangerously slow heart rate. This needs a vet straight away.

Drops and ointments that contain a steroid are risky for a different reason. Steroids can slow or stop healing when the surface of the eye is damaged, so an ulcer that looked like simple pink eye can quickly get much worse. Leftover medicine from a previous episode, or from another pet, carries the same risk. What helped last time may not help now, and it could be harmful. Before prescribing anything that contains a steroid, your vet usually checks for an ulcer with a dye test.

How vets diagnose it

The main question is whether conjunctivitis is the whole problem or a sign of something else. Your vet will look at the eyelids, the third eyelid and the surface of the eye, often with a bright light and magnification. Common tests include the following.

• A Schirmer tear test, a small paper strip placed under the lower eyelid for one minute to measure tear production
• A fluorescein stain, an orange dye that shows up scratches and ulcers on the cornea
• Eye pressure measurement, to check for glaucoma and uveitis
• Sometimes swabs, tear duct flushing, allergy tests or a small biopsy

If the problem keeps coming back, your vet may refer your dog to a veterinary eye specialist.

Treatment

Treatment depends on the cause, and it often combines more than one approach.

• Foreign material is removed from the eye.
• Allergic and irritant cases often improve with gentle rinsing using a sterile eyewash, avoiding triggers such as smoke and dust, and anti-inflammatory or antihistamine drops. Dogs with allergies affecting the whole body often need treatment for the skin allergy as well.
• Dry eye is usually treated with drops that stimulate tear production, such as cyclosporine or tacrolimus, along with lubricants. Treatment is usually lifelong.
• Eyelid and eyelash problems are often corrected with surgery.
• Antibiotic drops or ointment are used when there is pus-like discharge or a bacterial infection, together with treatment of any underlying problem.
• Ulcers, glaucoma and uveitis need their own, more intensive treatment.

Most dogs with conjunctivitis do very well. Long-term causes such as dry eye, allergies and immune conditions can usually be controlled, although they need ongoing care and regular checks.

Caring for your dog at home

Follow your vet's instructions closely, and finish the full course of medicine even if the eye looks better sooner. If the eye looks worse, or your dog starts squinting, call your vet rather than waiting for the next check.

• Wipe away discharge gently with a clean cotton pad moistened with lukewarm water or the eyewash your vet recommends. Use a fresh pad for each eye.
• Stop your dog from rubbing the eye. If scratching is a problem, ask your vet about a protective cone.
• Keep your dog away from smoke, dust and sprays while the eye heals.

If an infection such as distemper might be involved, keep your dog away from other dogs until your vet says it is safe.

Prevention

Keep vaccinations up to date, since distemper and canine adenovirus can both affect the eyes. After walks in long grass, check the eyes, ears and paws for grass seeds. Keep smoke, dust and sprays away from your dog, and work with your vet to keep skin allergies under control.

Some breeds are more prone to dry eye, including American cocker spaniels, English bulldogs, Lhasa Apsos, West Highland white terriers, Cavalier King Charles spaniels, shih tzus and pugs. Mention any thick discharge or a dull-looking eye at checkups. Watery eyes with brown staining are often a different issue, explained in our guide to tear stains and blocked tear ducts.

Eye problems in rescued dogs

Dogs living on the street are exposed to dust, smoke, plant material, fights and infections, and they may never have been vaccinated. At Paw Squadron, every animal we rescue sees a vet, gets a checkup and is dewormed, so problems such as eye infections can be picked up early. A new home can still bring new dust, plants and allergens. If your adopted dog develops red or weepy eyes after arriving, a visit to your own vet is the sensible next step.

For more guides on eye problems and everyday care, browse PawPedia. If you adopted from us and have questions, write to us from the Contact page.