Causes of Canine Conjunctivitis and Treatment Options

Conjunctivitis affects many dogs – and it has many causes.

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Something is wrong with your dog’s eye. It’s bright red or oozing pus or itching like crazy. Could it be pink eye? This common childhood condition, also known as red eye or conjunctivitis, affects people, cats, and our canine companions.

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Conjunctivitis is an inflammation of the conjunctiva, the tissue covering the eye and inner surface of the eyelid. If caused by bacteria or viruses, it can be infectious. Noninfectious conjunctivitis can be caused by allergic reactions, irritants, or trauma injuries.

While contagious conjunctivitis is common among cats and schoolchildren, most canine cases involve seasonal allergies or pollen exposure, injuries like cuts or scratches, or the presence of a small foreign object – anything from a grain of sand to a sliver of bark, piece of grass, tiny leaf, or small insect. In those cases, secondary bacterial infections may develop.

According to veterinary ophthalmologist David T. Ramsey, DVM, “Primary conjunctivitis attributable to infectious pathogens is exceedingly rare in dogs. In contrast to canine conjunctivitis, feline conjunctivitis is almost always primary and attributable to infectious pathogens (viral, chlamydial, or bacterial). Bacterial conjunctivitis in dogs almost always occurs secondary to an underlying disease that alters normal resident conjunctival flora and favors bacterial proliferation.”

Getting a Correct Diagnosis
The symptoms to watch for are eye redness, discharge, swelling, squinting, excessive blinking, sensitivity to light, pawing the eyes, or rubbing the face and eyes on floors, the ground, or other surfaces.

If you think your dog might have conjunctivitis, see your veterinarian. An eye exam can rule out corneal diseases, disorders of the tear ducts or tear production, eyelid abnormalities, or parasites of the conjunctiva or eyelids. It is important to get an accurate diagnosis because what works for simple conjunctivitis will not treat these more serious underlying problems.

Your veterinarian may perform certain tests, such as fluorescein staining to detect corneal ulcers or superficial abrasions, the Schirmer tear test to determine whether your dog is producing sufficient tears, and a thorough exam of the external eyelids, third eyelid, and conjunctiva.

If needed, additional tests can check for specific bacteria, the distemper virus, glaucoma, and other illnesses.

Treatment may include thorough rinsing or irrigation to remove foreign objects or irritating substances, medication to correct insufficient tear production or eyelid infections, antibacterial eye ointments for secondary bacterial infections, or anti-inflammatory eye medications to help reduce swelling.

Types of conjunctivis include:

-Serous conjunctivitis, which is a mild (not serious) condition, causes membranes to look pink and swollen, with a clear, watery discharge. This condition is usually caused by irritants such as dust, allergens, and cold or windy weather.

-Allergic conjunctivitis, a form of serous conjunctivitis, can cause itching. Household chemicals, lawn and garden sprays, and smoke from cigarettes or wood-burning stoves or fireplaces are potential causes of serous conjunctivitis. While foreign objects tend to affect a single eye, environmental factors that cause allergic conjunctivitis often affect both eyes.

-Keratoconjunctivitis sicca, or dry eye (also known as KCS), contributes to irritation, inflammation, and infection. The conjunctiva is usually red and inflamed, and symptoms may include squinting; a thick, ropey, mucous-like discharge; and corneal scarring.

-Follicular conjunctivitis, also known as mucoid conjunctivitis, results when small mucous glands (follicles) react to an infection or eye irritant and form a rough, cobblestone surface that irritates the eye. The resulting discharge resembles mucus, and if the problem persists, the rough surface can be a chronic irritant. Puppies and young dogs are typical follicular conjunctivitis patients, and the illness usually subsides with age.

-Purulent conjunctivitis is usually associated with Streptococcus and Staphylococcus bacteria. Thick secretions of pus and mucus may form a crust on the eyelids.

-Neonatal conjunctivitis affects the eyelids of infant puppies before or after their eyelids separate, which usually happens at 10 to 14 days of age. During or shortly after birth, bacteria may move behind the eyelid. Prompt veterinary treatment is important because untreated neonatal conjunctivitis can result in corneal damage and blindness.

-Parasitic conjunctivitis is rare in North America, but in some cases bot fly larvae or, in the Western United States, the parasitic worm or nematode Thelazia californiensis can inhabit the conjunctival sac between eye and eyelid. Eyeworms, as they are commonly called, are transmitted to dogs by insects. Both adult and larval eyeworms can produce symptoms ranging from mild tearing or discharge to conjunctivitis, keratitis (inflammation of the cornea), or corneal ulcers.

Other causes
In addition to injurious conditions like corneal ulcers and keratitis, blepharitis (inflammation of the eyelids) and skin diseases that affect the eyelids can all contribute to conjunctivitis. 

Some upper respiratory diseases, including kennel cough, involve viruses and bacteria that can produce conjunctivitis in one or both eyes along with coughing, sneezing, lethargy, decreased appetite, fever, and nasal discharge.

In some dogs, conjunctivitis is caused by anatomical irregularities, such as loose or drooping eyelids that cannot close completely, or eyelids that roll inward, or lashes that grow in the wrong direction, any of which can cause lashes to rub against the cornea.

Treatment
If you suspect that your dog has something trapped in her eye, don’t waste time. Flush the eye with a sterile saline solution or, if that isn’t possible or effective, go to your vet right away. An irritating foreign object can create serious eye problems if left untreated, especially if the dog is doing her best to dislodge it.

Underlying problems that result in conjunctivitis should always be treated. For example, artificial tears and lubricants help dogs with keraconjunctivitis sicca, or dry eye, along with topical antibiotics to resolve bacterial infections or concurrent corneal ulcers.

Abnormal eyelids or eyelashes can be treated surgically.

Conjunctivitis accompanying upper respiratory infections is typically treated with topical antibacterial medication and supportive care.

Allergic reactions can be challenging because dogs, like people, can be allergic to all kinds of things. But if your dog is diagnosed with allergic conjunctivitis, it’s a good idea to protect him as much as possible from cigarette or wood smoke, spray-on carpet cleaners, lawn chemicals, and harsh cleaning products. Change furnace and air-conditioner filters frequently, and experiment with air purifiers or humidifiers to see if they help prevent symptoms.

Parasitic conjunctivitis requires the physical removal of eyeworms or larvae, which can be accomplished by flushing the conjunctival sac with sterilized saline or by removing them with a fine forceps or cotton swab while the dog is sedated. Treatment with a parasiticide such as moxidectin is reported to be even more effective than mechanical removal, especially where eyeworms are endemic.

Home First Aid
Sterile saline solutions are widely available, and the same products can be used to rinse foreign objects or irritants from the eyes of both canine and human patients. For general first aid, keep a sterile eye rinse on hand.

Most natural food markets and some pharmacies sell eye washes for pets. For example, Espree Natural Aloe Optisoothe Eye Wash for Dogs & Cats contains purified water, aloe vera, benzalkonium chloride, and sodium chloride; V-Pro Eye Rinse for Dogs contains boric acid, purified water, sodium borate, and sodium chloride; and the human product OcuFresh Eye Wash contains sodium chloride, sodium borate, and boric acid. All of these can be used to flush a dog’s eyes.

If you don’t have one when you need it, you can make a simple saline eye wash with 1 cup distilled water and 1 teaspoon salt, boiled for 5 minutes and then cooled to room temperature. This solution should be freshly made and stored in the refrigerator for no more than a day or two before use.

Willard Water concentrate, described in “Willard Water: A Powerful Anti-oxidant” (WDJ June 2006), has helped many dogs recover from eye injuries and infections. Simply add a small amount of the concentrate (about 1/2 teaspoon concentrate per cup of water) to your saline solution. To be sure the solution is completely clear, strain it through a paper  coffee filter before applying.

It often takes two people to rinse a dog’s eyes, one to hold the head steady and one to keep the dog in position. For best results, tilt the dog’s head to one side so that the rinse flows from one side of the eye to the other.

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Homemade or purchased eye wipes can be used, although they should not be applied directly to the eye, but rather used around it. To make your own, simply saturate cotton balls or a cotton pad and dab around the eye. Solution released from the cotton will rinse the eye.
A sterile spray bottle can also be used as well. Simply spray a fine mist of solution over the eye area. Even if the dog’s eyes are closed, some will enter the eye.

Treating Conjunctivitis at Home
The easiest form of this disease to treat at home is serous conjunctivitis. Infection-fighting ophthalmic gels and rinses, such as Vetericyn products, are sold through veterinary clinics and pet supply stores. Some come with a cone-shaped applicator that helps control delivery.

Herbal eye drops, which can be made at home or purchased at most pet supply or natural food stores, can help in many cases. Pet Alive’s Eye-Heal herbal eye wash contains burdock, greater celandine, meadowsweet, and rosemary. Animals’ Apawthecary Eye & Nose Herbal Drops contain sodium chloride, boric acid, sodium borate, and extracts of certified organic goldenseal, eyebright, and usnea. Halo Cloud Nine Herbal Eye Wash contains eyebright extract, goldenseal extract, boric acid, and sea salt. NHV Ey-Eas eye drops contain chamomile, eyebright, goldenseal, and rosemary in a base of purified water and glycerine.

Several eye-friendly herbs are effective, gentle, and well tolerated by most canine patients. To brew any of these herbs as a tea (called an infusion), add 1 teaspoon dried herb to 1 cup boiling water, cover, and let stand until cool. Add 1 teaspoon unrefined sea salt, if available, or any table salt.

Alternatively, dilute the tea with any over-the-counter saline solution labeled for eye use. You want the result to be slightly salty, like tears.

Add 1/2 teaspoon Willard Water concentrate if available. Strain the mixture through paper coffee filter to remove any plant parts or undissolved salt. Apply with an eye dropper, cotton balls, or spray bottle every two to three hours as needed.

-Calendula (Calendula officinalis) is among the first herbs to consider for minor first aid. A broad array of medicinal compounds in the flowers of the plant, including various essential oils, flavonoids, saponins, triterpene alcohols, and carotenes, combine to help speed cell reproduction and inhibit bacteria and fungi at the site of injury. For minor cuts, insect bites, abrasions, or post-surgical incisions, a calendula wash will bring quick, soothing relief to pain and swelling, while lending antimicrobial properties to the body’s healing effort. Cool calendula tea works well as an eye wash for conjunctivitis, where its mild but predictable astringency combines with bacteria-fighting properties to reduce irritation and infection.

-Chamomile, both the German (Matricaria recutica) and Roman (Chamaemelum nobile) varieties, is considered one of the safest and most versatile herbal pet remedies. Because of its anti-inflammatory properties, chamomile is often recommended as an eye wash ingredient. Follow the tea-brewing instructions above and apply when cool.

-Nettle (Urtica dioica) has so many medicinal properties, it’s considered an all-purpose healing aid. As herbalist Gregory Tilford wrote in “Learning about Nettle” (WDJ, May 2003), “Nettle is one of the first herbs I reach for when a need arises for a soothing, anti-inflammatory eye rinse.”

-Raspberry leaf (Rubus idaeus) is another soothing herb that helps reduce the discomfort caused by conjunctivitis. Best known as a uterine relaxant and whelping aid, red raspberry leaf is an astringent herb containing polypeptides, flavonoids, and tannins. Its tea works well as a first-aid rinse for cuts and abrasions.

-Goldenseal (Hydrastis canadensis) is a key ingredient in some eye drops because it is both anti-inflammatory and antimicrobial. This makes it especially appropriate for conjunctivitis that is secondary to bacterial or fungal infections. Goldenseal quickly reduces inflammation and redness. Because the plant part used is the root rather than leaves, goldenseal tea should be brewed as a decoction rather than an infusion. Combine 1 cup water with 1 teaspoon chopped dried root, cover, bring to a boil, and simmer over low heat for 20 minutes, then remove from heat with cover in place and let cool to room temperature.

-Oregon grape root (Mahonia aquifolium) fights infection and reduces inflammation, making it another herb appropriate for the treatment of conjunctivitis. Prepare as a decoction, like goldenseal. Because the berberine in this solution can irritate the eyes, dilute this tea with an equal or greater part of chamomile or raspberry leaf tea, some other soothing infusion, or a saline solution.

-Cornflower (Centaurea cyanus) tea is a traditional eye wash in parts of France. Its mild astringent and antiseptic qualities make it effective in the treatment of conjunctivitis and inflammation.

Don’t Bother With These Remedies
Although Eyebright (Euphrasia spp.) is widely recommended as an herbal eye treatment, and although it is astringent and has antibacterial properties, there is no scientific evidence showing that eyebright is effective against conjunctivitis or any other eye disease, and Germany’s Commission E (an agency that documents the effectiveness of herbal preparations and approves or disapproves their use) recommends against using it. In addition, eyebright is considered an at-risk herb because of over-harvesting. Most herbalists agree that eyebright can safely be eliminated from herbal eye formulas.

Another widely recommended product that has not been shown to be effective against conjunctivitis is colloidal silver. This solution, in which minute particles of silver are suspended in water, has been marketed for decades as a natural infection-fighter and as a treatment for conjunctivitis. In 2004, the Journal of Wound Care published a study in which three different colloidal silver solutions had no effect on the growth of test organisms. 

Support Therapies
In addition to treatments that address conjunctivitis directly, consider some with a less obvious healing connection.

When Chloe, my eight-year-old Labrador Retriever, developed a bright red left eye with an oozing white discharge, her veterinarian, Tia Nelson, DVM, diagnosed conjunctivitis. Her symptoms developed in December, when many dogs in Montana’s Helena Valley experience seasonal allergy symptoms in response to smoke from wood-burning stoves and fireplaces, and they appeared the day after we went for a very cold, windy hike. Because Dr. Nelson is also a veterinary chiropractor, she adjusted Chloe’s neck and jaw, explaining that eye conditions often respond to alignment corrections.

Acupuncture is another supportive therapy. As Randy Kidd, DVM, wrote in “The Structure of the Eye” (WDJ, September 2004), “Acupuncture has been successfully used to treat many eye conditions. Keratitis, chronic conjunctivitis, and all sorts of eye irritations typically respond favorably to acupuncture, and cataracts or even blindness may respond.”

He explained that an acupuncturist might diagnose conjunctivitis as an example of excess heat of the liver. Acupuncture needles positioned to bring the liver back into balance would then restore the body to a state of harmony.

Various energy healing therapies, such as Reiki and Jin Shin Jyutsu, are also used to restore balance and health to the body. When Chloe’s symptoms developed, canine massage therapist Adele Delp performed Jin Shin Jyutsu around her eye.

We also applied NHV Ey-Eas eye drops. Chloe’s eye quickly returned to normal.

Freelance writer CJ Puotinen lives in Montana. She is the author of The Encyclopedia of Natural Pet Care and other books.

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