Why Are My Dog’s Eyes Red? (Vet-Written Article)

Filed in Dog Health by on August 3, 2021

why are my dogs eyes red

My eyes get red after a late-night binge-watching my favorite series, or after a day of gardening in pollen season. There’s also something about seeing a dog’s red, irritated eyes that makes my own eyes water.

Have you ever looked at your dog’s red eyes and wondered if they have spring allergies too, or if they have the occasional sleepless night? Our furry pals can develop red eyes for a variety of reasons, and some are critical emergencies.

If you are asking, “Why are my dog’s eyes red?” keep reading for possible answers. It may be time to grab the leash and head to your vet. Your dog’s vision could depend on it.

Here are some common conditions causing red eyes in dogs:

  • Allergic Conjunctivitis
  • Irritants
  • Foreign Body
  • Corneal Ulcer
  • Infection
  • Dry Eye
  • Cherry Eye
  • Glaucoma
  • Uveitis

As a veterinarian, when I see “red eyes” on the appointment schedule, these are the conditions that I begin thinking about. Let’s explore each one to see if your dog’s eyes fit the description.

Allergic Conjunctivitis

Ah-choo! When pollen counts are high, we reach for the tissues and antihistamines. Our furry friends can suffer during allergy season too. Environmental allergens may include pollen, dust mites, and molds.

Most dogs with allergies will feel itchy, causing them to scratch their bodies, lick and chew their paws, and shake their ears.

Although sneezing isn’t a common allergy symptom in dogs like it is in people, dogs may develop allergic conjunctivitis.

The lining of the eyelids, or conjunctiva, will look bright pink and a little swollen. A clear or yellow discharge may be present.

Your veterinarian may prescribe antihistamines and eye drops, or other allergy medications to provide relief for your red-eyed pooch.


puppy on a dirty carpet

Just as our eyes become irritated in a smoky environment, so do our dogs’ eyes. Other irritants include carpet or other household cleaners, construction dust, dirt, and perfumes or air fresheners.

Cigarette smoke and campfire smoke can both lead to red, irritated eyes.

Foreign Body

Veterinarians get really excited when we can significantly help your dog within the span of a short appointment.

I had that rewarding experience recently when a spunky chihuahua came to see me with a week’s duration of a red, goopy, squinting eye.

After numbing the eye, I set to work cleaning out the “goop” and matted hairs to investigate. He had a corneal ulcer, which we’ll cover next, but that wasn’t all.

There appeared to be a fine hair sticking out from under his eyelid. I tried to extract it with no luck.

I finally turned his eyelid inside out and pulled out a large grass awn! I can’t imagine how painful this must have been. It was truly the highlight of my week to remove it.

Other foreign bodies may include cat claws, dirt, other plant material, pieces of toys or carpet, fish hooks, and the dog’s own hairs or lashes.

Corneal Ulcer

The cornea is the eye’s clear windshield. The cornea can become damaged by a foreign body, an object transiently scratching or poking, a misguided eyelash, or an eyelid tumor.

Entropion, or inward rolling eyelids, can also lead to scratches on the cornea. These scratches can become infected.

Corneal ulcers may also result from dry eye, infections, and genetic conditions. Deep ulcers can even lead to rupture of the eye.

Your veterinarian can apply fluorescein stain to your dog’s cornea to diagnose an ulcer. Treatment involves removing any underlying cause, as well as removing dead tissue, and applying medication.

They may recommend a contact lens or surgery for temporary protection.


conjunctivitis in dog

Conjunctivitis may be caused by a viral or bacterial infection. The approach to a healthy active dog with red, puffy eyes will be different than to a lethargic, sick dog.

Viral infections such as canine distemper virus may cause conjunctivitis, but the whole dog will need to be treated.

A bright and active dog with yellow discharge from the eyes may have a bacterial infection requiring a course of antibiotic ointment. Foreign bodies and ulcers may lead to eye infections.

Dry Optic

Dry eye, also called keratoconjunctivitis sicca (KCS), is a condition where the tear glands fail to make adequate tears. Tears are essential for keeping the eye lubricated and healthy.

Secondary infections and corneal ulcers are common with dry eye. A copious thick white or yellow discharge is often pasted around the eye.

Causes of dry eye include immune-mediated tear gland destruction, drug reaction, injury, and viral infection.

Your veterinarian can diagnose dry eye with a Schirmer tear test. Treatment typically involves topical medication.

Surgery to move the salivary gland duct to the eye can be performed in some cases. The smell of steak may make your dog cry!

Cherry Optic

dog with cherry eye

You’ve heard the phrase “apple of my eye,” but what about “cherry eye?” Cherry eye, also called Prolapsed Gland of the Third Eyelid, can appear as a shiny red mass at the lower medial corner of the eye.

This tear gland normally hides in the third eyelid, but when it prolapses forward, it can’t be missed. The third eyelid is the triangular white flap that originates at the inner corner of the eye. It may cover more of the eye when something is wrong.

Certain breeds are predisposed to the condition such as the Boston terrier, bulldog, and beagle, but any breed can develop a cherry eye.

Treatment involves surgically replacing the gland. Recurrence may happen, and one possible side effect of a cherry eye or its treatment is dry eye.


Glaucoma, a condition involving increased intra-ocular fluid pressure, is a very painful medical emergency.

It may be genetic, or secondary to conditions such as a luxated lens or inflammation. Glaucoma may lead to blindness, so a suddenly red painful eye means grab those keys and head to the nearest veterinary emergency clinic.


The uvea includes the iris, ciliary body, and choroid. When any part of the uvea becomes inflamed, the eye will appear red.

You may see a tiny pupil, clouding inside the eye, and excessive squinting. Uveitis may be caused by a viral, tick-borne, or fungal infection, trauma, lens problems, and more.

Just like glaucoma, uveitis is painful and requires immediate veterinary attention.


I hope you’ve learned some useful information on why your dog’s eyes may appear red. There are other causes, but these are some of the more frequent reasons why a pooch will come visit me to investigate red eyes.

Always have your veterinarian diagnose your dog’s red eyes, and let them prescribe the medication. Don’t use your own eye medication on your dog, please!

Together, you and your veterinarian can develop a plan to give your dog back those healthy puppy-dog eyes.

About the Author

Dr. Jacqueline Dobranski, DVM is a contributing writer to Dog Endorsed. She received her D.V.M. from Cornell University College of Veterinary Medicine in 1997, and her B.S. from Cornell in 1992. She earned a Graduate Certificate in Shelter Animal Medicine in 2015. Dr. Dobranski currently practices small animal medicine in the Washington DC area.

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