Red Eyes in Dogs: 13 Causes Explained by a Veterinarian

Red eyes in dogs can be a symptom of many different eye conditions, some more serious than others. To help dog parents sort out what red eyes might mean for their dog, integrative veterinarian Dr. Julie Buzby discusses the potential locations and appearance of the redness, 13 causes of red eyes in dogs, and what to expect at the vet visit. Plus, she reviews the treatment options and prognosis for a dog with red eyes.

Most of us know how miserable red, irritated eyes can feel. Whether it’s allergies, dry eyes, smoke exposure, or simple exhaustion, eye discomfort has a way of affecting our entire day. The same is likely true for our canine companions.

Red eyes in dogs can develop for many different reasons, ranging from mild irritation to painful injuries or underlying medical conditions. Unlike humans, dogs can’t say something when their eyes hurt. Thus, it’s important that dog parents recognize the early signs of discomfort and seek care when needed.

What are red eyes in dogs?

The term “red eyes” can refer to a pink to red discoloration anywhere in, on, or around the eyes. For example, you might notice red lines or spots on your dog’s eye or a bloodshot appearance to one or both eyes. Or there could be hazy or clumpy redness inside the eye itself, or a pink to red discoloration of the eyelids and tissues around the eye. All of those variations fall under the category of “red eyes.”

Plus, depending on the underlying cause, dogs may have one form of eye redness or several at the same time.

Which parts of a dog’s eye can become red, and what does it look like?

Several areas in and around a dog’s eye can become red. The location and appearance of the redness matter because they help narrow down the cause.

Red sclera (episcleral injection, scleritis, or episcleritis)

The sclera is the white, fibrous part of the eye that makes up much of the globe. Scleral redness, or episcleral injection, results from enlargement of the tiny blood vessels that supply this tissue. As the vessels get bigger, they make prominent straight red lines on the sclera. If these tiny vessels burst, you may also see small areas of hemorrhage. They look like red dots or paint splatters on the white sclera.

Episcleral injection is usually due to an internal eye issue like glaucoma or uveitis. However, immune-mediated diseases, tumors, infections, and eye injury can sometimes cause focal or diffuse inflammation of the sclera (scleritis) or tissue between the sclera and conjunctiva (episcleritis).

Red conjunctiva (conjunctivitis)

The conjunctiva is the pink tissue that lines the eyelids, reflects onto the surface of the globe, and covers the dog’s third eyelid. When the conjunctiva becomes inflamed, the tissue appears red and swollen (chemosis). Sometimes the vessels may also look more prominent. The third eyelid may stay elevated to protect the cornea. Discharge may also be visible from the affected eye, which can indicate inflammation (usually clear, watery discharge) or infection (thick yellow or greenish discharge).

Red conjunctiva tends to indicate a problem on the exterior of the eye, such as irritation, infection, allergies, foreign material, or trauma.

Subconjunctival hemorrhage

Dogs can experience bleeding beneath conjunctival tissue, called a subconjunctival hemorrhage. It looks a bit like a blood blister that covers much of the white part of the eye. Trauma, strangulation, being strongly restrained, or spontaneous bleeding due to poor clotting ability may all lead to a subconjunctival hemorrhage.

Redness on the surface of the cornea (corneal neovascularization)

The surface of the cornea (clear windshield of the eye) can sometimes become red or pink as well. While the cornea doesn’t normally contain any blood vessels, some may start to grow across it with corneal ulcers, internal diseases (glaucoma or uveitis), or corneal inflammation (keratitis). They start at the junction of the sclera and cornea and progress across the cornea.

Redness within the eyeball (hyphema)

Bleeding inside the front of the eye (hyphema) may result from trauma, high blood pressure, infection, the presence of a tumor, or a clotting disorder. When you look at your dog’s face, you may notice a uniform red glow to the eye(s). Or you might see a streaky area of settled blood in the bottom of the eye, sort of like a snow globe before you shake it up.

Without prompt treatment, hyphema can cause the pressure inside the eye to increase. This, in turn, can lead to permanent eye damage and loss of vision if the retina and optic nerve are also affected.

Redness of the periocular (around the eye) tissues

Inflammation of the sensitive tissues of the eyelids and facial skin surrounding the eyes can also be a reason your dog has red eyes. You may notice the skin feels warm and puffy. And there may be abrasions or scabs on the skin if your dog has been pawing at the affected eye. It’s also not uncommon to see focal areas of hair loss, especially if your dog is rubbing the eye excessively. 

This type of irritation isn’t always eye-specific. But it often develops in dogs secondary to excessive pawing at the face or excessive rubbing of the face on furniture, carpeting, or grass. Common causes include allergies, insect bites, and exposure to caustic chemicals that irritate the skin.

What other symptoms may accompany red eyes?

In many cases, dogs will have a range of symptoms that go far beyond just red eyes. They include:

• Pawing at the face or rubbing the face on the carpet: These behaviors often lead to redness, irritation, and a loss of fur around the face and eyes. They can also cause further damage to the eye.
• Squinting or holding the eye closed (blepharospasm): Due to pain and/or light sensitivity, dogs with corneal ulcers, foreign material in the eye, glaucoma, or other conditions may be reluctant to open the eye.
• Discharge: An increase in eye discharge (clear) often accompanies environmental allergen exposure. In contrast, thicker, colored discharge (yellow or green) often develops in the face of dry eye or bacterial or viral infections.
• Corneal changes: Dogs’ corneas should normally appear clear and glassy on observation. However, discoloration of the corneal surface (cloudy, blue tint, or new vessel growth) may develop due to trauma, chemical and physical irritants, or systemic metabolic or autoimmune disorders. 
• Eye enlargement or protrusion: Increased prominence or size of the eyeball could be due to:
  • Exophthalmos: A growth or pocket of infection behind the eyeball pushes it forward.
  • Proptosis: The eyeball pops completely out of the eye socket, usually due to trauma.
  • Buphthalmos: The eyeball itself is larger due to chronic stretching from glaucoma.
• Anisocoria (uneven pupils): Pupils of unequal size can be red flags for many focal and systemic disorders. Depending on the condition, the pupil may be dilated or constricted in the affected eye.
• Pain: Dogs with painful eyes are often head shy, ducking away from attempts to touch the face or examine the eyes.
• Changes in vision: Corneal discoloration, hyphema, retinal detachment or degeneration, glaucoma, or cataracts may all cause temporary or permanent loss of vision.

When are red eyes in dogs an emergency?

In many cases, if your dog suddenly develops red eyes, he or she needs to be seen by a veterinarian. Squinting or holding the eye closed, cloudiness of the cornea, signs of eye pain, swollen or protruding eyes, hyphema, unequal pupil size, vision loss, and severe redness of the eyeball all indicate the need for rapid care, whether with your regular vet or via an emergency vet visit. Very mildly red but otherwise normal-looking and comfortable eyes are generally not an emergency, but may still require care.

Eyes can go from bad to worse rapidly, and your dog’s sight can be at stake. Thus, if you are worried about your dog’s red eyes, the best thing you can do is call your veterinary team for advice or head to the ER.

What causes red eyes in dogs? 13 possible causes

There are a number of possible causes of red eyes in dogs. Some dogs may have a problem involving the eye. Other dogs may have a systemic condition leading to redness of the eye and/or surrounding tissue plus symptoms elsewhere in the body.

1. Foreign objects or irritants in the eye

Inflammation of the eye may result from irritants or foreign objects coming in contact with the sensitive surface of the eye. Some potential culprits include:

• Tiny irritants: Pollen, dust, dirt, smoke, or mold
• Larger foreign objects: Grass seeds, plant material, twigs, foxtails in dogs, or small pieces of glass
• Chemical irritants: Sprays, fragrance diffusers, shampoos, and ear cleansers

Dogs with red eyes due to inflammation may have visibly swollen blood vessels on the surface of the eye, a generalized pink or red discoloration of the conjunctiva and eyelids, swelling of the lids, and, in some cases, clear or whitish discharge. They may also squint or paw excessively at the eyes.

2. Corneal ulcers

In some cases, the foreign object, trauma to the eye, or the dog’s scratching and rubbing at the eye in response to inflammation can lead to damage to the surface of the cornea called a corneal ulcer in dogs. In addition to the conjunctiva appearing red, the dog may also have a cloudy spot on the eye and be holding the eye closed. With more chronic ulcers, you may also notice small vessels starting to grow across the cornea.

3. Infections

Infectious diseases and eye infections may both lead to red eyes in dogs

Some infectious diseases, including canine herpesvirus, distemper, adenovirus, and upper respiratory infections (dog catching a cold), can cause red, swollen conjunctiva. In most cases, though, dogs with these infections usually show other signs of illness as well. Respiratory symptoms like coughing, sneezing, nasal discharge, or congestion are particularly common.

Additionally, eye infections in dogs may occur secondary to a different eye problem such as a corneal ulcer, dry eye, or eyelid abnormality. It is rare for a dog to develop a bacterial eye infection without some sort of inciting cause, though.

4. Trauma

Any injury involving the head, face, or eye can cause redness, swelling, and eye pain in dogs. Common examples include:

• Bites or scratches from another animal
• Puncture wounds from sticks or other objects in the yard
• Blunt force trauma such as being hit by a car
• Dog bee stings or bug bites on dogs that occur around the eyes or face. 

Depending on the source of trauma, the eye may look inflamed or have swollen vessels visible on the sclera. Or it might have a red shadow in the front of the eye (hyphema) or blood on the skin around the eye.

In extreme cases of trauma, the eyeball may pop out of the socket (proptosis) so that it is sitting in front of the eyelids like a googly eye. Or the eye may rupture, which causes it to look deflated and smaller than normal.

5. Allergies

Dogs can experience allergic reactions to a multitude of environmental irritants, including pollen, dirt, grasses, dust, house mites, and mold. Exposure to these allergens can lead to itching, discharge, conjunctivitis, chemosis, and irritation of the skin around the eyes.

That being said, skin issues tend to be the most common manifestation of a dog’s seasonal allergies.

6. Abnormalities of the eyelids

Both inherited and acquired eyelid disorders can contribute to eye redness in dogs. Some examples of include:

• Entropion in dogs—Eyelids that roll inward so that the eyelashes rub the cornea.
• Ectropion—Eyelids that roll outward, creating a pocket between the lower lid and eyeball.
• Cherry eye in dogs—Third eyelid gland pops out of position and looks like a tiny cherry in the inner corner of the eye.
• Dog eyelid tumors— Masses like meibomian gland cysts may develop at the eyelid margin and irritate the eye.
• Blepharitis—Inflammation of the eyelids due to allergies, parasites, infections, etc.

Eyelid issues often cause swelling and inflammation around the eyelids, which may get worse if the dog rubs or paws at his or her face excessively. Additionally, growths on the eyelid margin, entropion, or ectropion can cause conjunctival inflammation, pain, infections, or corneal ulcers.

7. Anterior uveitis

Anterior uveitis in dogs is a type of inflammation that targets structures in the front part of the eye, namely the iris and ciliary body. (The iris is the colored portion of the eye and the ciliary body lies directly behind it.) As these structures become inflamed, dogs may experience episcleral injection, painful eyes, and light sensitivity (photophobia). In some cases, you might see cloudy eyes in dogs or blood inside the front of the eye (hyphema). Discharge may also be present in the corners of the dog’s eyes.

Problems involving the eye, such as cataract development, tumors, trauma, and exposure to chemical irritants, can trigger uveitis. But so can systemic conditions like infectious diseases, autoimmune diseases in dogs, and high blood pressure.

8. Dry eye (keratoconjunctivitis sicca)

In keratoconjunctivitis sicca (KCS or dry eye in dogs), a decrease in tear production causes the corneal surface to become dry and irritated. Plus, goopy eyes in dogs (thick green to yellow mucoid eye discharge) and conjunctivitis are common. Sometimes the eye discharge gets stuck to and irritates the eyelids and surrounding skin. Due to discomfort, dogs with KCS may paw at their face or rub their eyes, leading to scratches or hair loss around the eye.

In more advanced stages, dogs may have neovascularization and/or dark pigmentation on the surface of the eye.

9. Glaucoma

Glaucoma in dogs occurs when a dog’s intraocular pressure (IOP) becomes higher than normal. The end result is extreme eye pain, enlargement of scleral vessels (episcleral injection), and a cloudy cornea due to fluid accumulation (corneal edema). Left untreated, or sometimes even with treatment, glaucoma can result in blindness, continued pain, and/or loss of the eye.

10. Lens luxation

When the lens inside the eye loses the ligamentous attachments that hold it in place, it can fall forward or backward. Displacement of the lens forward can interfere with the drainage of fluid from the eye necessary to maintain a normal IOP. As a result, pressure may build quickly inside the eye. This causes pain, a red sclera, changes in pupil size or shape, frequent blinking and pawing at the eye, and ocular discharge.

In some cases, movement of the lens from its normal position and the change in the direction of light reflection to and from the back of the eye may cause the eye to have a red glow.

11. Hypertension (high blood pressure)

Hypertension in dogs (high blood pressure) can lead to retinal damage or bleeding into the retina or chambers of the eye. In severe cases, blood pools in the anterior or posterior chambers, making the inside of the eye look red. Plus, the dog may experience eye pain, eventual blindness, and systemic consequences if the hypertension isn’t addressed.

12. Tumors

Whether benign or malignant, tumors within or behind the eye may progress to the point where they cause a painful, red eye with increased pressure and loss of vision. Certain eye tumors may also metastasize to other organs like the liver and kidneys. This leads to decreased organ function and a decline in the dog’s overall health.

13. Miscellaneous medical conditions

Some medical conditions may increase the risk of a dog developing glaucoma, uveitis, or other causes of red eyes. Alternatively, the redness could be from the original condition itself. Examples include:

• Diabetes in dogs
• Hypothyroidism in dogs
• Clotting disorders
• Cancer like lymphoma in dogs
• Autoimmune disorders such as uveodermatologic syndrome or pannus in dogs

 In these situations, usually both eyes are affected. Depending on the underlying cause, you may see episcleral injection, conjunctivitis, hyphema, periocular redness, or other forms of red eyes.

Which dogs breeds are prone to red eyes?

Dogs of any size, breed, and age can develop red eyes due to one of the many conditions we just discussed. 

That said, brachycephalic dog breeds such as Boxers, Boston Terriers, French Bulldogs, and Pekingese are a bit more at risk for abnormal tearing issues, periocular irritation, and enlargement of the eyes. This is the case due to their facial conformation and prominent globes. 

Additionally, there are breed predispositions for some of the causes of red eyes. For example, Cocker Spaniels are prone to glaucoma, and several terrier breeds are predisposed to lens luxation. Your vet can help you understand which eye problems your dog might be more prone to.

How will the vet find the cause of your dog’s red eyes?

Many eye conditions can have similar symptoms. Thus, determining the cause of your dog’s red eyes often takes some detective work on the part of your vet.

Gathering a history

At the start of your appointment, the veterinary team will collect a history for your dog. This includes asking about when the symptoms started and if there was a specific incident or event that may have triggered the problem. Plus, they may inquire about any prior eye issues or non-eye symptoms you have noticed.

Eye exam

After the physical examination, your vet will conduct an ophthalmic exam on your dog. The specific testing routine may vary depending on your dog’s comfort level, but typically includes:

• A thorough evaluation of your dog’s eyelids, eyelash margins, corneas, lenses, iris margins, anterior and posterior chambers, and other relevant eye structures.
• Schirmer tear test (STT) to evaluate tear production (helps diagnose dry eye).
• Application of fluorescein stain to look for a corneal foreign body or ulceration.
• Intraocular pressure (IOP) testing using a tonometer. Conditions like glaucoma, extraocular masses, or hyphema cause an elevated IOP, while a decreased IOP may point to uveitis.
• A fundic exam to evaluate the vessels, retina, and optic nerve in the back of the eye. (This exam may happen at the same time the vet is assessing the structures closer to the front of the eye.)

Additional diagnostics

Depending on these results, your vet may recommend additional testing. This could include an ocular ultrasound if he or she suspects an abscess or tumor behind the eye, cytology and culture if infection is present, or a biopsy of a mass outside the globe, on the lids, or associated with the third eyelid gland. Sometimes your regular vet performs these tests. Other times, he or she may refer you to a veterinary specialist (ophthalmologist) to continue the workup.

What is the treatment for red eyes in dogs?

Treatment depends greatly on the underlying cause of the red eyes. But the overall goals are to address the problem itself and improve the dog’s comfort. This may involve medical treatment or surgical intervention.

Medical treatment for red eyes

Medical treatment is a good option for many causes of red eyes. It isn’t possible to list the specific treatment for each condition here, but your veterinarian can help you understand what your dog’s case will require. Generally speaking, though, medical treatment may involve:

Management of mild irritation

Dogs with mild eye redness and irritation due to something like allergies or an irritant in the air may only need over-the-counter eye washes and warm or cold compresses. Plus, it can be helpful to keep the face free of ocular discharge, which can mat the fur and cause skin irritation.

However, this doesn’t mean you should try that approach before heading to the vet. Because eyes can worsen rapidly, it is safest to consult your vet so he or she can provide an accurate diagnosis and an appropriate treatment plan.

Addressing infection, inflammation, and pain

For dogs with an infection or more severe inflammation, the vet may recommend prescription eye drops or ointments. Common eye medications include antibiotics, steroids (if no corneal ulceration is present), or topical non-steroidal anti-inflammatory drugs (NSAIDs). For dogs who need additional pain relief, your vet may also prescribe oral anti-inflammatories or pain medications.

Managing chronic eye conditions

There are topical and systemic medications that can help lower the IOP in cases of glaucoma. Dogs with dry eye may benefit from a medication to stop the immune system from attacking the tear glands (the most common cause of KCS). Those treatments may need to continue long-term depending on the underlying cause of the KCS or glaucoma.

Wearing an Elizabethan collar to protect the eye

If your dog is painful and paws or rubs his or her eyes excessively, using an Elizabethan collar (E-collar) can help prevent further injury to the eye during your dog’s recovery.

Contact lenses for dogs with deep corneal ulcers

Dogs with deep or extensive corneal injuries or ulcerations may also benefit from a collagen contact lens or a traditional contact lens. Both options help protect the surface of the eye while it is healing. They do need to be removed by your veterinarian when the treatment and recovery period are complete, though.

Treatment for systemic diseases

If your dog has a systemic disease like diabetes mellitus, hypothyroidism, a clotting disorder, or an autoimmune condition, addressing it may help resolve or minimize eye redness.

Chemotherapy or radiation

If a tumor is present but the eye is still visual, the veterinary oncologist may sometimes recommend chemotherapy or radiation. He or she can let you know what is right for your dog.

Surgical options for red eyes in dogs

There are some eye conditions that require surgery for the best results. In other situations, surgery may become a consideration if medical treatment does not resolve the issue. Surgical techniques that are useful for eye disorders include:

• Pocket techniques (like the modified Morgan pocket) to replace a prolapsed third eyelid gland (cherry eye) into its normal position.
• Debridement and grid or diamond burr keratotomy to facilitate healing of indolent (non-healing) corneal ulcers.
• Temporarily suturing the upper and lower eyelids together (temporary tarsorrhaphy) to form a protective barrier for corneal ulcers, post-surgical corneal grafts, trauma to the eye, or proptosis.
• Enucleation (surgical removal of the eye) if the eye has been traumatized beyond repair, for glaucomatous eyes that are painful and non-visual, or if a tumor is present within the eye.
• Conjunctival graft to protect and bring a blood supply to deep or melting corneal ulcers.
• Eyelid surgery to remove a mass or correct entropion or ectropion.

This is not an exhaustive list. Your vet or veterinary ophthalmologist can let you know if surgery is right for your dog.

Are there home remedies for red eyes in dogs?

With the possible exception of mild eye irritation that resolves quickly with eye wash, red eyes in dogs need veterinary care, not home treatment. Eyes can worsen quickly, and many conditions are painful. Thus, it is important to have an accurate diagnosis from the veterinarian and the appropriate treatment approach.

How can you prevent red eyes in dogs?

It isn’t possible to prevent all causes of red eyes. But the following tips may help decrease the risk of some of them happening to your dog.

1. Keep dog-safe eye flush on hand in case you need it to remove an irritant or foreign object from your dog’s eye.
2. Use dog-specific facial wipes to remove discharge from the facial folds as a regular part of your dog’s bathing routine. And use them when your dog has more “eye goop” than usual.
3. Install HEPA air filters in your home to reduce airborne allergens and irritants that may cause your dog (and you) to have red, itchy, or watery eyes.
4. Purchase protective eyewear like Doggles® for your dog to wear during outdoor activities. Doing so can significantly reduce the risk of foreign material getting into your dog’s eyes. Many dog goggles also help reduce exposure to UV light, something that is helpful for dogs with some autoimmune eye disorders.
5. Keep your windows and doors closed to minimize the introduction of pollen and dust inside the home. This is an especially good plan during peak allergy seasons.
6. Make it a habit of looking at your dog’s eyes on a daily basis so you can catch changes quickly. If something seems off, contact your vet for advice.

What is the prognosis for dogs with red eyes?

The prognosis for dogs suffering from painful, red eyes depends largely on the underlying cause. For uncomplicated infections, allergies, or mild trauma, the prognosis is typically excellent for a return to normal comfort and vision. However, for more complex or chronic issues such as glaucoma, severe corneal ulcers, systemic illness, or cancer, the prognosis will depend on how your dog responds to the comprehensive treatment plan.

When it comes to red eyes, don’t wait

Time is of the essence with eye problems in dogs due to the potential for pain, loss of vision, or loss of the eye itself. Because the eyes are so delicate and sensitive, any change in your dog’s eyes deserves careful attention.

If your dog suddenly has red eyes, seems painful, starts squinting, rubs at his or her face, or behaves differently than usual, contacting your veterinary team promptly is the safest choice. Early treatment can go a long way toward protecting your dog’s comfort and vision.

Why did your dog have red eyes?

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