The causes of red, inflamed eyes in dogs vary considerably, from mild allergies to sight-robbing health conditions, to serious systemic infections.
Red eyes can be a symptom of a serious systemic disease, so a complete physical exam and sometimes laboratory tests are an important part of determining the cause and treatment.
Hay Fever and Allergies
Allergic conjunctivitis often occurs when the pollen count is high. Dogs, like humans, can suffer from “hay fever” and allergies, causing mild-to-moderate inflammation and itchiness of the tissues surrounding the eyeball.
Allergic dogs can be so uncomfortable they rub their eyes, introducing bacteria and causing infection and/or causing a painful scratch or abrasion on their cornea (the clear tissue at the front of the eye). Corneal ulcers may be superficial and heal quickly with treatment. Left untreated, they can become deep and very serious. Best to have us check it out.
Corneal ulcers, caused by an abrasion to the cornea, will also cause a dog’s eye to become reddened and inflamed. Corneal ulcers are not uncommon in social dogs that frequent doggie day cares, dog parks, and sometimes grooming salons.
They occur more frequently in “smooshy-faced” (brachycephalic) breeds whose eyes are more exposed, such as French bulldogs, Shih Tzus, English bulldogs, Boxers, Boston Terriers, and Pugs.
Bacteria, Viruses, and Uveitis
Reddened eyes can also be infectious, ranging from a potentially contagious bacterial infection (“pink eye”) to serious viral upper respiratory infections, like canine influenza and canine distemper.
Viral upper respiratory infections will be accompanied by a fever and other symptoms, and may make dogs very ill.
Uveitis (inflammation within the eyeball) can be caused by an autoimmune disease, trauma to the eye, or very serious systemic infections, such as leptospirosis.
Anything rubbing on the eyeball can cause inflammation and discomfort, and can lead to secondary problems such as infection and corneal ulcers.
Distichiasis is when an eyelash growing in the wrong place (such as on the inside of the eyelid) causes irritation to the eye.
Other times, a Meibomian gland in the lash line goes rogue and grows into a mass that rubs on the eye.
Glaucoma, Dry Eye, and Eye Tumors
Some health conditions causing red eyes are very serious and need immediate treatment.
Glaucoma (increased pressure within the eye), can rob a dog of its sight.
Keratoconjunctiva sicca, or “dry eye” is an autoimmune disease decreasing normal tear production, making a dog’s eye extremely painful and damaging the cornea, also robbing a dog of its sight if left untreated.
Tumors and growths within the eyeball can also cause the eye to become reddened and need to be diagnosed and treated quickly.