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Squinting, Tearing, or Discharge from the Eyes in Cats and Dogs

Common Causes

More common causes are listed first.   Less common causes are listed later.

  • In cats, upper respiratory infections are the most common cause of squinting and tearing. Often, sneezing, sinus congestion, and nasal discharge are noted concurrently.
  • In dogs, conjunctivitis is the most common cause of squinting, redness of the eye, and discharge from the eye.
  • Minor trauma to the eye can cause redness, discharge, and squinting.
  • Ulcers, or abrasions on the surface of the eye, can cause eye pain, redness, and discharge.
  • Foreign objects, such as foxtails, will cause severe irritation, swelling, and squinting when lodged in the eye.
  • Dry eye, also known as KCS (short for keratoconjunctivitis sicca) will cause redness, discomfort, and mucus to appear in the eyes.
  • Pets with shallow eye sockets that cause the eyes to protrude (such as Persian cats, Pugs, or Boston Terriers) often develop a brown discoloration in their eyes. This syndrome is known as pigmentary keratitis.
  • Prolapse of the third eyelid gland (commonly known as cherry eye) can cause apparent redness and swelling of the eye.
  • Cataracts cause the eyes to change to a white color.
  • A number of rare syndromes cause changes in the color or appearance of the eyes. In most of these syndromes, the changes are caused by deposits of cells, fat, or protein on the eye.
  • Exposure to caustic or inflammatory substances may cause swelling, redness, and tearing of the eyes.
  • Allergic reactions can lead to redness, pain, and tearing from the eyes.  However, these types of reactions are much less common in pets than in people.

Recommended Course of Action

Seek veterinary attention as soon as possible for any pet who has irregularities with an eye.  The eyes are very sensitive organs.  Many of the syndromes listed above can cause pain or vision loss if not treated.

Copyright © Eric Barchas, DVM All rights reserved.
The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.