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Also Known As

Pink eye


Conjunctivitis in horses is similar to conjunctivitis in humans. The tissues of the horse's eyes become irritated by allergens, excessive dust, flies, injury, or a combination of irritants. When bacterial infection sets in, the eyes appear red and watery. Often the nasolacrimal (tear) duct becomes infected, and it is necessary to call in a veterinarian to flush the tear duct and prescribe treatment to clear up the infection.

Because conjunctivitis accompanies more serious conditions, it should be given immediate attention if it does not clear up quickly with saline solution treatment.


  • Inflammation of the mucous membrane or pink lining that surrounds the eyeball
  • Increase in redness of eye tissues
  • Swelling and watering of eyes
  • Sticky, yellowish discharge
  • Refusal of horse to open eye(s) or repeated clenching of eyelids


Conjunctivitis may be caused by any number of irritants, including dust, pollen, insect bites, flies, allergens, viral infection, or it may also be the result of injury to the eye.


Removing known irritants from the environment is the first step in preventing conjunctivitis. Keeping dust of all kinds at a minimum, having an insect control plan in place, and taking care to prevent injuries to the horse's eyes will help lessen the problem.

In the case of ongoing or repeated cases of the disease, a face shield may help solve the problem without having to use drugs or chemicals.


In cases of simple conjunctivitis, saline solution treatment is often effective. Saline is a sodium chloride solution available over-the-counter at drug stores. If this doesn't clear the problem, it may be necessary to have a veterinarian flush the nasolacrimal (tear) duct.

If corneal ulcers are causing the problem, a veterinarian should be called in to diagnose the problem fully and to treat the ulcers with topical antibiotics and atropine. Sometimes a topical corticosteroid, such as dexamethsasone, may be used by the veterinarian in the treatment. Fungal corneal ulcers may be present, and tests will be necessary for a definitive diagnosis.

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EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.