You probably know the common signs of conjunctivitis in dogs, a condition commonly called pinkeye. The area surrounding the eye turns pinkish, usually accompanied by tearing, swelling and discharge. Don't simply apply topical over-the-counter eye medications to your dog's eye. Take him to the veterinarian for an examination and diagnosis. Various factors cause canine conjunctivitis, and your pet's vision is at risk if you don't know the reason for the eye problem.
Infection, whether viral or bacterial, is probably the most common cause of canine conjunctivitis. If both eyes are involved, suspect infection. If your dog is up to date on his shots, he's unlikely to come down with conjunctivitis caused by the canine herpesvirus, distemper or adenovirus. The more likely culprit is bacteria, especially corynebacterium or mycoplasma. If your dog's eye discharge contains pus or mucus, your vet likely will prescribe eye ointments containing antibiotics for treatment.
Conjunctivitis can indicate your dog is suffering from certain eye diseases. Common eye diseases in which conjunctivitis is a symptom include keratoconjunctivitis sicca -- often referred to as dry eye -- glaucoma and uveitis. Some breeds are prone to hereditary eye diseases, such as episcleritis, in which conjunctivitis is characteristic. Collies, golden retrievers and cocker spaniels have this genetic predisposition, which can lead to vision loss. Treatment of eye disease depends on the diagnosis, and your vet might refer your dog's case to a veterinary ophthalmologist.
Conjunctivitis can result from eye or eyelid abnormalities. These include entropion, where the dog's eyelid folds inward, causing constant discomfort. Besides pinkeye, entropion symptoms include excess tearing and constant squinting. Less common but also causing conjunctivitis is the opposite condition, ectropion, in which the eyelid folds outward. Blocked or inflamed tear ducts can cause conjunctivitis, as can distichiasis, or an inward-growing eyelash. Conjunctivitis occurring because of eye abnormalities requires correction of the problem, which includes surgery.
If your dog suffers from seasonal allergies, whether from mold, pollen or other substances, conjunctivitis might be part of his annual ordeal. Conjunctivitis can result from other allergic triggers, such as perfumes, cigarette smoke or insecticides. Your vet likely will conduct skin tests to get to the root of your dog's allergies, and prescribe medication to keep him comfortable during allergy season.
Foreign objects stuck in your dog's eye can cause the conjunctiva to swell and tear. Your vet will examine your pet's eye, removing any foreign items and prescribing medication to heal surface scratches.