Why Are Your Dog’s Eyes Red? Learn What Causes Red Eyes and How to Treat Them

Eyes are one of our most important assets, and that’s true for your dog, too. Dogs rely on their vision to eat, play, and explore, and so much more, including facial and emotional recognition, communication with other dogs, hunting and tracking, and depth perception. Therefore, you must regularly look at your pup’s eyes to assess whether they seem normal.  

Redness is one of the most common signs you will see if there is a problem with your dog’s eyes. Many conditions will include red eyes as a symptom ranging from mild irritations to serious medical emergencies requiring immediate attention. Here, I will explore the common causes of red eyes in dogs, the symptoms to watch for, how veterinarians diagnose a condition, the treatment options available, and how to decide if you should seek professional help.

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Common causes of red eyes in dogs

There are many different causes of red eyes in dogs. Some are harmless and temporary, while others are serious and need urgent care, so it’s necessary to know the cause to treat red eyes. As a pet parent, it is important to know about possible reasons so you can make the right decision if you wake up one morning and your dog's eyes are red.  

Allergies

Allergies in dogs are very common. While most of the time, symptoms of allergies in dogs involve the skin, dogs can suffer from red, irritated eyes just like people. Common allergens that affect dogs include:

• Environmental allergens: Examples include pollen, mold, dust mites, and smoke. Another name for this is atopic allergies. Many of the allergens are only around at certain times of the year, so they are also called seasonal allergies. It is helpful to tell your vet if your dog’s symptoms are present year-round or during certain seasons. 

• Food allergies: Certain proteins, grains, or additives are common allergens. Unlike environmental allergies, food allergies are usually year-round. That also can be a diagnostic clue. 

• Chemical irritants: Cleaning products, perfumes, and air fresheners can act as contact allergens, meaning contact with the skin can cause a reaction. A clue your dog may have contact allergies is symptoms that occur only on parts of the body that have direct contact with the allergen. This is less likely to cause red eyes. 

Symptoms of allergic reactions in dogs include red, watery eyes, but also pawing at the face, sneezing nasal discharge, skin rashes, and/or excessive blinking. Treatment for allergies typically includes antihistamines, special diets, avoiding the allergen if possible, steroids, and allergy injections. 

Eye infections

Bacteria, viruses, or fungi can cause infection in a dog’s eyes. Common symptoms are redness, swelling, squinting or keeping the eye closed, and/or thick yellow, green, or white discharge. Treatment often includes antibiotics, fungi or antiviral eye drops, oral medications, and proper eye hygiene. It’s important to get a diagnosis and start treatment quickly. Infections can lead to ulcers in the cornea. 

Dry eye syndrome (Keratoconjunctivitis sicca or KCS)

Dry eye syndrome occurs when a dog’s tear glands cannot produce enough tears. The symptoms will include redness, a thick mucus-like discharge, repeated infections, chronic dryness, and irritation. Without enough lubrication, the eye’s surface becomes susceptible to infection and damage. 

Causes of KCS include autoimmune disorders, certain medications, and trauma to the tear glands. Treatment involves artificial tear supplements, cyclosporine eye drops, or surgery in severe cases. 

Conjunctivitis (pink eye)

You have undoubtedly experienced or heard about pink eye or conjunctivitis. It is inflammation of the conjunctiva, the thin membrane that covers the eye and inner eyelids. Causes can include infections, allergens, or irritants. Conjunctivitis is one of the more common causes of red eye in dogs. 

Symptoms of conjunctivitis include redness and swelling, excessive tearing, and/or mucous or pus-like discharge. Treatment depends on the cause and may involve antibiotic or anti-inflammatory eye drops or ointment. 

Glaucoma

If the pressure inside the eye increases, it is called glaucoma, a severe condition that damages the optic nerve and can lead to blindness. Glaucoma can occur in one eye or both eyes. If it occurs in one eye, it often will affect the other eye eventually. It is diagnosed by an instrument that measures the pressure in the eye when placed directly on the cornea. 

Symptoms of glaucoma include red, bloodshot eyes, cloudiness in the cornea, bulging or swollen eyeball, vision loss, and/or pain. It is an emergency that requires immediate treatment. The vet will give your dog medications to lower the eye pressure or surgical intervention.

Eye injury or trauma

Dogs are naturally curious and active, engaging in rough play with other dogs and running through bushes or tall grass.  This makes them prone to eye injuries. Symptoms of an eye injury include sudden redness, swelling and discomfort, and/or excessive tearing. Treatment depends on the severity of the injury, ranging from eye drops to surgery. 

Corneal ulcers

An ulcer is an open sore on the cornea, the eye's surface. Corneal ulcers can be mild or quite serious. They are often caused by dry eye syndrome, trauma, or infections. Symptoms of corneal ulcers include, intense squinting, excessive tearing, sensitivity to light, redness, and/or swelling.

If an ulcer is severe enough or not treated promptly, your dog can have complications, even vision loss. Treatment includes medicated eye drops and, in severe cases, surgery. If medication is the treatment of choice by your vet, be patient. Corneal ulcers can take a long time to heal.

Foreign bodies

Foreign objects can become lodged under a dog’s eyelid. This often includes dust, dirt, grass seeds, or small debris. Signs of a foreign body include excessive blinking or squinting, redness and swelling, and/or watery discharge. Foreign bodies often require veterinary removal and antibiotic eye drops to prevent infection.

Entropion 

Entropion is a painful condition in which a dog’s eyelids roll inward, causing the eyelashes to rub against the eye's surface. This causes constant irritation, resulting in redness, pain, and ulcers. Entropion is common in Bulldogs and Shar-Peis. It usually has to be corrected with surgery. 

Uveitis

Uveitis is inflammation of the inner part of the eye. Autoimmune diseases, trauma, or infections can cause it. It is a painful condition that can lead to blindness if untreated. It is usually easy to recognize because of its cloudy appearance. 

Symptoms include severe redness, squinting, cloudy appearance, and/or low ocular pressure. Treatment involves anti-inflammatory and antibiotic medications.

Tumors

Tumors can occur anywhere on the body, including the eyes. Eye tumors, whether benign or malignant, can cause redness, swelling, and vision changes. It will most likely be obvious if the tumor is on the outside of the eye, including the eyelids or conjunctivitis. If it’s a part of the iris, the color will change. If the tumor is in the back of the eye or behind the eye, you may only see the symptoms, not the actual tumor. Treatment depends on the tumor type and location and includes surgery, radiation, or chemotherapy.

High blood pressure (hypertension)

When a dog’s blood pressure is high, the eyes may be red because of ruptured blood vessels in the eye. Hypertension is often associated with underlying conditions such as kidney disease, heart disease, and hyperthyroidism. Treatment focuses on managing the underlying condition and regulating blood pressure.

Blepharitis

Blepharitis is inflammation of the eyelids, often caused by infections, allergies, or immune system disorders. Symptoms include swollen, crusty eyelids and excessive blinking.

Bacterial infections are the most common cause of blepharitis. These infections often result from trauma or scratches around the eye, chronic skin infections (pyoderma), and/or poor hygiene in skin folds (especially in brachycephalic breeds). Dogs with bacterial blepharitis may exhibit swollen, red eyelids, pus-like discharge from the eye, and/or crusting or scabbing around the eyelids.

Treatment involves warm compresses, medicated eye drops, and managing the underlying cause. Other than bacterial infections, the following are also causes of blepharitis:

• Fungal or parasitic infections can also contribute to blepharitis. Some of the most common culprits include certain yeasts, mites, ticks,  and fleas

• Allergic reactions 

• Frequent pawing or rubbing at the eyes

• Autoimmune diseases

• Hormonal imbalances and endocrine disorders

• Eyelid abnormalities (congenital or acquired)

• Certain breeds are prone to eyelid conditions that can predispose them to blepharitis, such as Bulldogs, Pugs, Cocker Spaniels, and Shih Tzus.

• Seborrheic dermatitis. Breeds predisposed to seborrhea include Golden Retrievers, West Highland White Terriers, and Basset Hounds.

• Tumors or growths on the eyelid

• Poor hygiene and environmental factors

• External factors that contribute to blepharitis include excessive exposure to dust, smoke, or pollution, poor grooming habits (especially in long-haired breeds.), dirt or debris accumulating in facial folds (e.g., Bulldogs, Shar-Peis)

What are the most common symptoms of red eyes in dogs?

Beyond redness, symptoms that may indicate an eye problem include:

• Excessive tearing

• Thick or discolored discharge

• Squinting or sensitivity to light

• Pawing or rubbing at the eyes

• Cloudy or bluish appearance

• Vision loss or bumping into objects

How vets diagnose the cause of red eyes in dogs

Veterinarians use various diagnostic tools, including:

• Fluorescein staining: Stain is applied to the eye's surface to detect corneal ulcers.

• Tonometry: Measures eye pressure for glaucoma.

• Schirmer tear test: Evaluates tear production.

• Bloodwork and imaging: Identifies underlying conditions such as thyroid disease, kidney disease, or diabetes. 

Sometimes, a vet can identify conditions just by looking at them. 

Treatment for red eyes in dogs

Treatment depends on the cause and may include:

• Antibiotic or antifungal eye drops for infections

• Artificial tears for dry eye

• Surgery for entropion, tumors, or severe injuries

• Medications for glaucoma and uveitis

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When you should seek help for dog red eyes

Seek immediate veterinary care if your dog’s red eyes are accompanied by:

• Sudden onset of redness

• Severe pain or swelling

• Vision loss or behavioral changes

Bottom line

Eyes are enormously important. When they turn red, it indicates there is a problem. Red eyes in dogs can have many causes, from minor irritations to severe medical conditions. If you don’t know if a veterinarian is needed, err on the safe side and see a veterinarian right away. Prompt veterinary care is crucial for protecting your dog’s vision and well-being. If redness persists or worsens, absolutely seek professional help.

References

• Patterson-Kane, J C, et al. “Mixed Germ Cell Tumor in the Eye of a Dog.” Veterinary Pathology, vol. 38, no. 6, 1 Nov. 2001, pp. 712–714, https://doi.org/10.1354/vp.38-6-712.

• Thomasy, Sara. “Canine Conjunctivitis: Causes and Treatment.” British Small Animal Veterinary Association EBooks, 1 Apr. 2020, pp. 62–62, https://doi.org/10.22233/9781910443774.6.1.

• Woerdt, Alexandra. “The Treatment of Acute Glaucoma in Dogs and Cats.” Journal of Veterinary Emergency and Critical Care, vol. 11, no. 3, Sept. 2001, pp. 199–204, https://doi.org/10.1111/j.1476-4431.2001.tb00084.x.