Pink Eye in Horses

Conjunctivitis in Horses

Much like humans, horses can contract conjunctivitis (inflammation of the conjunctiva which is a part of the eye), also known as pink eye. It may be due to several factors such as a dusty environment, an illness, or a viral or bacterial organism infecting the eye. Depending on the cause, it can be also highly infectious.

Conjunctivitis is normally associated with a clear or yellow/white discharge in the eye. It may or may not contain mucus. At the same time, itching and irritation are also clear signs of the beginnings of conjunctivitis and these symptoms may appear before others symptoms arrive.


  • Redness of the eye
  • Discharge (clear, yellow, or with mucus)
  • Irritated eyelids
  • Swollen eyelids
  • Closed eyelids or squinting
  • Adverse reaction to bright light
  • Adverse reaction to dust
  • Rubbing the eyes or shaking the head


  • Infection of the conjunctiva
  • Inflammation of the uvea (uveitis)
  • Numerous organisms responsible for infection – may be of viral (herpesvirus) or bacterial origin
  • Secondary infection to an underlying illness
  • Result of damage or trauma to eye
  • Lack of or insufficient tear production
  • Abnormally shaped eyelid
  • Face flies (bacterial transmitters)
  • Environmental irritants (i.e., dust, heat, dryness, pollen, other allergies)


A simple examination of the eye is often enough for a veterinarian to make an initial diagnosis of pink eye in the horse, since the symptoms are outwardly obvious. Following that, your doctor will perform a thorough physical and ophthalmological exam on your horse, taking into account the background history of symptoms and possible incidents that might have led to this condition.

Some of the tests that may be used in the diagnostic process are cultures of the discharge that is seeping from the eye, tissue scrapings, and fluorescein stain, a technique that uses a non-invasive dye, which illuminates portions of the surface of the eyeball that have been injured due to abrasions or the presence of foreign objects.


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