What causes discharge from your dog’s eyes?

The most common causes of eye discharge include:


Canine conjunctivitis is when the lining of the eyelids become inflamed. The most common sign of conjunctivitis is cloudy, yellow, or greenish discharge from one or both eyes. Your dog may also be squinting, and you’ll likely see redness or swelling around the eyes.

Conjunctivitis has many causes including bacterial infection, virus, allergies, trauma and tumors. In order to treat conjunctivitis, your veterinarian will need to determine the underlying cause. Your dog may need eyedrops, antihistamines, or antibiotics to treat the inflammation.

Conjunctivitis is a common cause of colored eye discharge, and your dog will often squint as a result of the inflammation.


Epiphora is the fancy word for “watery eyes.” You may notice your dog has an excessive amount of tear production. This is actually more common in brachycephalic (flat faced) breeds such as pugs and bulldogs, but can happen to any dog of any shape or size.

If your dog’s tear ducts are unable to expel the excess tears, they will build up, making it look like your dog is crying. The excess tears can sometimes cause a skin infection around their eyes, so it’s important to have your veterinarian assess the source. Epiphora may be a sign of conjunctivitis, allergies, or a problem with their tear ducts.

Dry Eyes (Keratoconjunctivitis Sicca or KCS)

What’s the opposite of watery eyes? Dry eye, of course! Officially called Keratoconjunctivitis sicca (or KCS for short), dry eye is exactly what it sounds like – eyes that lack lubrication are uncomfortable, itchy, and well, dry! Without proper tear production, the eyes are unable to flush away irritants, which can cause further damage if something gets in your dog’s eye. Your dog’s body will try to compensate for a lack of tears by creating mucus to lubricate the eyes instead.

Often this mucus is actually grey, as opposed to yellow or green like regular mucus. Since mucus does not function in the way that real tears do, the eyeball often becomes red and sore. KCS is commonly caused by eye infections, tear duct issues, or immune mediated disorders. Your veterinarian may prescribe some artificial tears once a diagnosis is confirmed.


Injury to your dog’s eye can occur from a multitude of reasons; running through tall grass or a forest, playing with another dog, being smacked in the face by the family cat. Even more subtle things such as dirt or debris can get lodged in their eye. Trauma may cause your dog’s eye to produce discharge, and your dog will likely scratch or rub their eye with their paw. Their eyeball(s) may appear bloodshot and sore.

Corneal ulcers can occur from trauma. They are wounds or abrasions of the cornea. The cornea is the transparent window that makes up the front surface of the eye. Some corneal ulcers are superficial and some are deep; both require veterinary care. Corneal ulcers are painful, so your dog will likely be pawing at their face or rubbing their face in the carpet, or holding their eye closed. If you suspect your dog has experienced trauma to their eye, seek veterinary attention right away.

Redness in the eyes is a common sign of abnormalities in the eye, including conjunctivitis, dry eye, and trauma.