Red Eyes in Dogs: What Are the Causes?

Red Eyes in Dogs: What Are the Causes?

Have ever had a problem with your dog’s eyes becoming red? Do you worry about allergies, irritation, or an infection causing redness in your dog’s eyes?

Your dog’s eyes could be red for many different reasons. Some of these reasons could be minor while other causes could be more serious.

Here are Some of the Most Common Causes of Red Eye in Dogs:


Conjunctivitis is a general term for inflammation of tissue around the eyes, and may be caused by different reasons. Some of the common reasons for conjunctivitis include allergies, bacterial infection, foreign material in the eye, or damage to eye itself such as an ulcer. Signs you may see with conjunctivitis include squinting and discharge from the eyes.

A fluorescent dye may need to be placed in the eye to pick up any ulcers that may have occurred. Topical medication with antibiotics and/or a steroid can help rule out it the redness is caused by an allergy or an infection.

Dry Eye (Keratconjunctivitis Sicca):

This medical condition causes red eyes because there is a reduction of tear production. Decreased tears causes the eyes to dry out and to become irritated. This can occur in dogs of all ages but some breeds can be predisposed to this disease.

Some predisposed breeds include cocker spaniels, bulldogs, Westies, Lhasa Apsos, and Shih Tzus.

Dry Eye can be caused by an immune related condition where the body attacks the tear glands in the eye. Other causes also include a birth defect and the result of a side effect of the antibiotic trimethoprim-sulfamethoxazole (TMS). A strip is placed in each eye to measure the tear production (Schirmer Tear test) to confirm a diagnosis. Once confirmed, most dogs will need to be placed on a long-term medication called cyclosporine to help with tear production.


Glaucoma is a condition characterized by increased pressure inside of the eye. This is caused by the failure of fluid to flow from inside to outside of the eye leading to the increased pressure. The increased pressure can cause intense pain, redness, and the affected eye to bulge.

In severe cases, the pressure increase can cause blindness. Diagnosis is made by checking the internal pressures of the eyes using a special tool called a tonometer. Sometimes glaucoma can be managed with various topical eye medications that help reduce pressure in the eyes. This is often a life time treatment. Unfortunately, most dogs who are diagnosed with glaucoma will eventually go blind.

Final Thoughts:

As you can see red eyes in dogs can be caused by different reasons. Some causes are easily treated while others may be more challenging and more involved. If your dog has red eyes, it is very important that he or she gets them checked out quickly by your veterinarian. This will ensure that the cause can be determined and properly treated.

Dwight AlleyneDwight Alleyne, DVM

Dwight Alleyne, DVM is the author of the Animal Doctor Blog, a blog that provides veterinary information about cats and dogs through articles and product reviews. He has almost 20 years of animal experience with 10 years as a veterinary technician and more than 9 years as a veterinarian. He currently practices in Georgia at a small animal practice where he provides veterinary services through surgeries and medical consultations. When he is not working, Dr. Alleyne enjoys spending time with his wife, daughter, and 7 year old cat named Queen.

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