Your dog’s eyes are as sensitive as your own, and as susceptible to irritation, allergies, injury, and disease. One of the earliest, surest signs of irritation is red eyes. If your dog’s eyes appear visibly red or swollen, it could be a sign of something as minor as an irritation or mild allergy, or as serious as eye disease.
Why Dogs’ Eyes are Sensitive
Dog eyes have a lot in common with your own: the eye is an active organ, constantly adjusting to light and focusing on objects in the environment. All the parts of the eye work together to produce images and relay them to the brain.
Dogs’ eyes differ from humans in that they have a third eyelid, the nictitating membrane, located in the inside corner of the eye. The third eyelid will extend up to protect the eyeball from scratches, or in response to inflammation. Dogs also have more rods in their corneas than humans do, which means they track light and movement better than you can (but overall their vision is less acute, and they don’t see as wide a range of colors).
As is the case with your eyes, external irritants can cause irritation, and disease can weaken or damage specific parts of your dog’s eye. Some types of dogs are more prone to eye issues than others, including :
– Brachycephalic, or flat-faced, breeds like bulldogs, shih tzus, and pugs
– Breeds with long hair around their faces, like poodles, maltese, and sheepdogs
– Older dogs, or dogs with existing health problems such as high blood pressure or diabetes
Causes of Red Eyes in Dogs
Redness, swelling, and discharge can indicate a wide array of issues for dogs, from harmless, mild allergies to something far more serious.
Some of the most common causes of red, bloodshot, and/or weepy eyes in dogs include :
– Eye injury or trauma, such as a scratch or foreign object in the eye
– Allergies (to food or environmental agents)
– Conjunctivitis, also known as “pinkeye” or “red eye.” An itchy inflammation of the tissue coating the eye, pinkeye is as common in dogs as it is in humans, and typically affects one eye at a time (source)
– Glaucoma, a fluid build-up in the eye that creates pressure which, if not alleviated, can cause blindness. Redness caused by glaucoma will be accompanied by visible swelling; learn more here.
– Dry eye syndrome (formally known as Keratoconjunctivitis sicca, or KCS). Dry eye can be caused by a number of underlying illnesses, so it’s important to have your dog checked out by a vet!
– Uveitis, a painful inflammation of certain parts of the eyeball
– Corneal ulcers, an erosion of the transparent, shiny membrane that makes up the front of the eyeball. Corneal ulcers are typically caused by trauma, such as getting scratched while running through brush.
Red eyes can also be caused by underlying medical issues like hyperthyroidism, diabetes, and some cancers. Of course, sometimes a red eye is simply a temporary reaction to a mild irritant! If you notice your dogs’ eyes look unusual, remain calm and consult a professional.