What you see. The starting point for addressing any equine health related issue is your observation.


Pink Membrane of Third Eyelid is Covering Eye(s)


The third eyelid is a membrane located at the inside corner of the equine eye. It slides over the eyeball from inside corner to outside corner and helps to protect the eye. In normal horses, the third eyelid is only visible as a pink rim at the inside corner of the eye.

Mild protrusion of the third eyelid can be a sign of dehydration. More prominent pink tissue here can indicate infection, cancer of the third eyelid, or other conditions. If the third eyelid is covering all or part of both eyes, it can indicate neurologic or neuromuscular disease. This is also a CLASSIC sign of tetanus.

The conjunctiva is loose pink lining tissue surrounding the eyeball. If it becomes very swollen, it can cover the eye. If the eye is punctured or shrinks, the surrounding tissues can cover it. Some chronic inflammatory and cancerous diseases of the eye cause a pink layer to develop over the eye.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
You also might be observing
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your role


What To Do

Regardless of cause, it is important to address this condition promptly. Assess your horse's general health using the Whole Horse Exam (WHE), and assess their hydration with a skin pinch. Take a photo of the problem and share it and your findings and concerns with your vet. Consider your horse's vaccination status. If you notice a stiff or strange gait, along with third eyelids covering the eyes, this is probably tetanus.

your vet's role

Your vet will try to determine whether this is a local problem affecting the third eyelid(s) or is a sign of systemic disease.
Questions Your Vet Might Ask:
  • Does your horse seem normal otherwise?
  • Are both eyes affected?
  • Can you make the problem worse by clapping your hands or flicking the skin of the face with a finger
  • How is your horse's attitude and appetite?
  • Has the horse had any other signs of a problem?
  • When did you first notice this?
  • When was the horse last given a tetanus vaccination?
  • Is the horse vaccinated for tetanus and other infectious diseases?
  • What are the results of the Whole Horse Exam (WHE)?

Diagnoses Your Vet May Consider

The cause of the problem. These are conditions or ailments that are the cause of the observations you make.

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Treatments Your Vet May Recommend

A way to resolve the condition or diagnosis. Resolving the underlying cause or treating the signs of disease (symptomatic treatment)

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Author: Doug Thal DVM Dipl. ABVP