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Home > Ask A Vet > Why Are My Dog’s Eyes Red? 13 Likely Reasons (Vet Answer)

Why Are My Dog’s Eyes Red? 13 Likely Reasons (Vet Answer)

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Dr. Paola Cuevas Photo

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Dr. Paola Cuevas

Veterinarian, MVZ

The information is current and up-to-date in accordance with the latest veterinarian research.

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As pet owners, we all become concerned if we notice something wrong with our beloved canine. If you have noticed a red eye or eyes on your dog, several factors could be causing it. We will review the 13 most common causes of red eyes in dogs and give you some valuable advice on how to handle it.

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The 13 Reasons Why Your Dog’s Eyes Are Red

1. Foreign Body in the Eye

We can all relate to this; a small object can enter our eyes and cause irritation. Dust, grass, hair, or a small flying insect stuck to the eye surface or under the eyelids can cause a red eye. A foreign body on the eye usually affects only one eye, with some exceptions. For example, if your dog was running around in a very dusty place, it might have gotten dust in both eyes. Try to visually inspect the eye, and if you see anything on the eye, you could try flushing the eye with a 0.9% saline solution. Chances are your dog might resist the treatment, or you might not feel comfortable doing it. In this case, make a quick visit to the vet. Once the foreign object is washed out, your dog’s eye will return to normal in a few hours.

Dog Eye Problem
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2. Allergies

Allergies are a common cause of red eye in dogs. Pollen, dust, weeds, mold, mites, and even food are common allergens that can cause red, itchy, and watery eyes. Sometimes, allergies are presented with other signs, such as runny nose, sneezing, and itchy skin. As part of the treatment, it is important to determine what the dog is allergic to. This can be done with a series of tests or with elimination diets. Your veterinarian will help you discover the cause of the problem. The treatment might include antihistaminic or anti-inflammatory drugs.

3. Conjunctivitis or Pink Eye in Dogs

Conjunctivitis is an inflammation of the conjunctiva, the clear layer of soft tissue covering the eye. This can be either infectious, caused by viruses or bacteria, or non-infectious, caused by allergens or irritant substances. Most cases of conjunctivitis are accompanied by puffy eyes or swollen eyelids, and they also present with some kind of abnormal eye discharge. The treatment will depend on the underlying factor causing it, so visit your vet to get an appropriate diagnosis of the cause.

vet checking dog's eyes
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4. Dry Eye (Keratoconjuntivitis sicca)

Like humans, dogs can suffer from dry eyes due to a lack of enough tear production. The veterinarian will perform a Schirmer tear test to evaluate the secretion level of the tear glands. It consists of placing a special paper strip on your dog’s eye and measuring the number of tears produced in one minute. If the tear production is insufficient and the diagnosis is dry eye, you will need to apply lubricating eye drops on your dog’s eyes a couple of times a day. Some cases will be resolved after a few days, but other cases are chronic. That means the dog will require eyedrops a couple of times a day for the rest of its life.

5. Dog Entropion

Another common cause of red-eye in the dog is entropion. This abnormality causes the eyelid to roll inward, so the eyelashes are rubbing against the eye, causing irritation, discomfort, and, in the worst case, ulceration of the cornea. The medical treatment for this condition is surgery.

dog with eye problem
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6. Distichiasis

In the case of Distichiasis, there is an extra set of eyelashes growing towards the inside of the eye. Like entropion, it causes irritation and can also lead to a corneal ulcer. The treatment is to remove or destroy the follicles of the abnormally growing eyelashes with electrolysis, cryotherapy, or surgery.

7. Corneal Ulcer

A corneal ulcer is the perforation of the thin, transparent layer on the eye’s surface. Corneal ulcers are very painful and can get infected. The possible causes are trauma, abrasions, substance irritations, dry eye, infections by bacteria, fungus or virus, and parasites. To diagnose a corneal ulcer, the vet will perform a fluorescein test applying a fluorescent green substance to the eye to see any potential perforation. The treatment will depend in part on the cause, but usually, the dog will need several eyedrops a few times a day, a cone collar to avoid further lacerations, and oral anti-inflammatory medication. Extreme cases could require surgery.

8. Blepharitis

Blepharitis is an inflammation of one or the pair of eyelids, affecting one or both eyes. Causes of this can be infection, trauma, irritation, or allergies. It could also be caused by a tumor. The vet will need to find out the cause of blepharitis to be able to treat it accordingly.

9. Cherry Eye

When cherry eye occurs, the nicitating membrane or third eyelid protrudes due to a tear gland that becomes inflamed and forces it out of place. A pink or red bump is visible, poking out from the lower eyelid. This ophthalmological condition needs surgery; the sooner, the better.

dog with cherry eye
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10. Uveitis

Uveitis is an inflammation of the uvea that consists of the iris, ciliary body, and choroid. Any or all three structures can become inflamed by infections of viruses, bacteria or fungi, and parasites. It can also be caused by toxins, irritations, trauma, high blood pressure, or metabolic disease such as diabetes. Treatment consists of decreasing the inflammation and treating the primary cause of this problem. If the vet diagnoses uveitis, your dog might be referred to a veterinary ophthalmologist because some cases are complicated and become recurrent.

11. Hyphema

Hyphema is blood trapped between the cornea and the iris. It is usually caused by trauma, but ulceration, hypertension, glaucoma, toxicosis, coagulation, or platelet disorders can also lead to this condition. Your vet will treat it depending on the causal factor.

dog with eye problem
Image Credit: Alexandr Jitarev, Shutterstock

12. Glaucoma

Glaucoma is a very painful condition in which the internal pressure of the eyeball is increased due to fluid buildup. Glaucoma damages the optical nerve and can cause blindness. The vet uses a specialized medical tool called a tonometer to measure the pressure of the eye. Early detection makes treatment easier. Sometimes topical treatment with eye drops can be used, but other cases need laser surgery.

13. Tumor

Tumors of the eyelids and glands can also cause red-eye in your dog. A variety of benign and malignant tumors can affect the different structures of the eye. The treatment depends on the kind and placement of the growth and varies from surgical removal to radiation, completely removing the eye (enucleation) in the most severe cases.

sick dog
Image Credit: Christin Lola, Shuuterstock



Red eyes in a dog can be caused by something as simple as a dust particle. But it can also be as serious as a tumor that requires the eye to be removed. If this happens suddenly and you can see a particle on the eye, rinsing out the eye with a saline solution should do the trick.

However, if the eye remains red after a couple of hours, it is necessary to visit the veterinarian to figure out what of the many possibilities is causing your dog’s eye to be red and find the appropriate treatment to resolve the issues before they complicate further.

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Featured Image Credit: Tatiane Silva, Shutterstock

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