Conjunctivitis is something you’re probably quite familiar with if you have kids. Or maybe you remember having “pink eye” as a child yourself. Either way, you know that the condition makes for a pretty uncomfortable situation. Our four-legged children are also susceptible to developing conjunctivitis, and although it’s not quite the same as it is in humans, it is still an unpleasant condition to endure.

Conjunctivitis, simply put, is inflammation of the conjunctiva, or the pink tissues lining the eyelids. The condition can occur for any number of reasons in our pets, but the end result is the same—one or both eyes appear red and swollen and have increased discharge. Often the affected eye is crusty and sometimes is even crusted shut. The eye will be itchy, so affected pets may paw at their eyes in an effort to provide relief.

Causes in cats

In cats, the most common cause of conjunctivitis is viral in origin. Herpes is an extremely contagious virus that is common in young kittens, especially those who are feral or are raised in crowded shelters. Kittens facing other stresses, like poor nutrition and external or internal parasites, are also prone to herpes virus infections. Herpes infections cannot be cured, but they can be managed. As such, adults who had herpes as youngsters will often deal with recurrent conjunctivitis in one or both eyes.

Bacterial conjunctivitis caused by chlamydial organisms are also common in young cats. Chlamydial infections in cats spread through close contact, such as is common in shelter situations. Respiratory infections caused by chlamydial organisms facilitate spread, as sneezing and coughing aerosolizes the infective organisms.

Causes in dogs

In dogs, bacterial infections are the most common cause of conjunctivitis. They are often a “one off” kind of infection, with no underlying cause. If chronic conjunctivitis is occurring in your dog, an underlying cause is probably to blame. Abnormal eyelid conformation, like entropion and ectropion, make the eye susceptible to this condition, as does the condition known as “dry eye”, or keratoconjunctivitis sicca.

Your veterinarian can usually diagnose conjunctivitis easily, but determining the underlying cause may take a few more diagnostic tests. Conjunctival scrapings can be viewed under a microscope to look for causative organisms, and especially stubborn cases may require samples to be sent away to a lab to determine what organisms are present and how best to treat the issue they are causing.

Your veterinarian will also check for corneal ulcers, which can often accompany the condition. Corneal ulcers add significantly to the discomfort experienced by patients with conjunctivitis, and because corneal ulcers can develop into a serious problem, frequent rechecks will likely ensue.


Conjunctivitis is generally treated with topical ophthalmic medications. Drops or ointments will vary depending on the underlying cause. Sometimes, oral medications will also be prescribed, especially in the case of viral conjunctivitis.

If your pet is being treated and does not appear to be improving, it’s time to schedule a recheck. Similarly, if your pet’s clinical signs worsen during treatment, contact your veterinarian right away.

Jan 23, 2014
Pet Health

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