The causes of bloodshot or red eyes in dogs vary considerably, from mild allergies to sight-robbing health conditions, to serious systemic infections.
Hay fever and allergies
When the pollen count is high, dogs can suffer from “hay fever” and allergies just like humans, causing mild-to-moderate inflammation and itchiness of the tissues surrounding the eyeball.
Rinsing may help
Sometimes, gently rinsing a dog’s eyes with sterile eye wash from the drug store is all it takes to provide comfort.
However, allergic dogs can be so uncomfortable they rub their eyes, introducing bacteria and causing infection and/or scratching the cornea (the clear tissue at the front of the eye), causing a painful abrasion. These abrasions can be superficial and heal quickly with treatment. Left untreated, they can become deep, occasionally causing a dog’s eyeball to rupture. Best to have us check it out.
Contagious eye infections, often called “pink eye,” are caused by a bacteria or virus. Pink eye is not uncommon in social dogs that frequent doggie day cares, dog parks, and sometimes grooming salons.
These infections may be contagious to humans – another great reason to bring your dog in to see us right away.
Eyelashes growing inside the eyelid
Anything rubbing on the eyeball can cause inflammation and discomfort, and lead to secondary problems such as infection and corneal abrasions. Sometimes, a tiny eyelash starts to grow on the inside of the eyelid, causing irritation.
Other times, a Meibomian gland in the lash line goes rogue and grows into a mass that rubs on the eye.
Sight-robbing health conditions such as glaucoma (increased pressure within the eyeball), high blood pressure, uveitis (inflammation within the eyeball itself), trauma to the eye or head, and “dry eye” (an autoimmune disease) can cause severe inflammation and need to be addressed right away. Left untreated, blindness can ensue.
Canine influenza and distemper
Serious upper respiratory infections, such as canine influenza and canine distemper, also cause dogs’ eyes to be red. These infections will be accompanied by a fever and other symptoms, and make dogs very ill.
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.