Why Are My Dog’s Eyes Red?

Dr. Jason Gagné, DVM, DACVIM
By Dr. Jason Gagné, DVM, DACVIM
Updated: 5/14/20242-4 minutes
A Basset Hound with droopy, red eyes

Your dog’s eyes can be as sensitive as they are precious. There are a range of causes that can make a dog’s eyes red, which we will explore below.

Some of these cause the skin or conjunctiva around the eye to appear inflamed and red, while others seem to affect the eyeball itself. As always, the best way to figure out the answer to the question, “Why are my dog’s eyes red?” is to talk to your vet as eye irritation can lead to more permanent damage if left untreated. But here are a few possible explanations you might hear mentioned during your appointment.

Causes of Red Eyes in Dogs


During the spring and summer months, human allergy sufferers will start experiencing the familiar sneezing, itchy eyes and runny nose. And while allergies can occur at any time of year, your four-legged family member might also be more prone depending on the season. 

Hay fever is also known to affect dogs and occurs when the body mounts an immune response to something that it has incorrectly identified as harmful, such as pollen in the air. To help with the irritating symptoms of canine hay fever, such as bloodshot eyes in dogs, talk to your vet about the best management plan for your pet. 

Eye Infection

If your dog has red eyes, it could be a sign of an eye infection. Eye infections in dogs can be caused by any number of things. Suffering an eye injury or coming into contact with bacteria can ultimately lead to an eye infection. Even a change in temperature or air quality can dry your dog’s eyes, making them more susceptible to an eye infection.

Environmental Irritants

There are plenty of potential irritants, both inside and outside of our homes, that can lead to red eyes in dogs. Perfumes, cleaning products, sprays, smoke and even dust can be culprits if they get into your pet’s eyes. So, if you’ve noticed your pet suffering from bloodshot eyes, it’s worth thinking about the possible irritants your friend crossed paths with on their daily adventures. Make sure you contact your vet, as well, because red eyes could also be a sign of something more serious going on; it’s best to rule out those concerns as soon as possible.


Could my pet havedog conjunctivitis? Does your dog have pink, watery eyes and swollen eyelids? Just like humans, dogs can get conjunctivitis. 

This condition occurs when the membrane covering the inside of the eyelids, known as the conjunctiva, becomes inflamed, and it can have many underlying causes, ranging from infectious disease to allergies or injury. Based on what has triggered your dog’s conjunctivitis, there are many treatment options available that will help alleviate symptoms.

Eye Injuries

Trauma to the eye is another possible explanation for why one of your dog’s eyes is red and swollen, all of a sudden. If you’ve got a particularly rambunctious pup in the family, you know how easy it is for them to bang into objects when playing and chasing. Your dog might also start squinting, which typically means they’re in pain. You might even notice bleeding. Contact the vet for help immediately if your dog is squinting or if you see any blood. If the blow to the eye was particularly hard, the cornea (surface of the eye) might have been affected, which can lead to painful ulcers developing on the eye itself. In turn, this can translate into scar tissue that obscures vision and can cause a range of other issues with eyesight. This is why early professional help is important.


Uveitis is the inflammation of certain structures in the eye that make up the uvea (this includes the iris, as well as some other middle layers of the eye). Unfortunately, this is a very painful eye disease, so you might see your pet avoiding bright light or keeping the affected eye shut.

Your vet will perform a series of tests to discover what exactly is causing your dog’s red eyes. This might include ultrasounds, blood tests and measurements of the fluid pressure inside the eye. If uveitis is indeed the culprit, the vet will recommend the appropriate treatment. In mild cases, you may see an improvement in your dog’s condition quite quickly, but frequent visits to the vet might be necessary to make sure the treatment is going to plan. More severe cases are less common, but could result in blindness, so it’s important to talk to a vet as soon as you notice any symptoms.

Corneal Ulcers

The membrane that makes up the front of the eye is called the cornea, and it can sometimes be scratched, especially if you have a dog that likes to get lost in tall grass or tends to bump into all sorts of objects when playing. Unfortunately, a scratched cornea is an invitation for bacteria to land on and damage it even further, causing a red eye and a lot of discomfort for our dear pooches. So, if your dog has bloodshot eyes, make an appointment with your vet for an eye examination to rule out a possible corneal ulcer. 


Could a simple case of red eyes in dogs hide a much more complicated condition, such as glaucoma? Although it’s more frequently diagnosed in older dogs, any dog can be affected. Cloudy eyes, redness and eye discharge are some of the most common symptoms owners should be on the look out for. Glaucoma is characterized by a buildup of fluid within the eye. It would be important to talk to a vet as soon as you notice these symptoms. Glaucoma can’t be reversed unless it’s caught in its very early stages, but there are many treatment options available depending on the severity of the condition. Find out more about glaucoma in dogs with our in-depth guide. 

Dry Eye

Sometimes a dog’s eyes are not producing enough moisture to keep the surface properly lubricated. As the tear glands dry up, the cornea becomes dry, too. With the moisture that once kept troublesome particles at bay gone, your dog’s eyes will become red and inflamed. Dry eye can have another health condition as its underlying cause, so consulting a vet is key in suitable management of this condition.

Cherry Eye

Cherry eye is a condition that affects a gland in the dog’s third eyelid. This gland will prolapse (pop out of its usual position) and can appear red and swollen giving the disease its name: cherry eye.

The exact cause is not clear, but cherry eye seems to appear more frequently in certain breeds, such as Bullmastiffs, Shar Peis, Cocker Spaniels and Great Danes

Foreign Object or Debris

Sometimes, the explanation for why your dog’s eye is red could be a foreign object. This can be quite common with the more adventurous canines. If your pooch loves to venture out and about in bushes and tall grass, they might get something in their eye that leads to redness and swelling. Foreign objects that end up in your dog’s eyes can be as small as a grass seed and as big as a part of a branch. Although it’s impossible to reduce the risk to zero, try to avoid long grass, and be sure to give your pooch a quick head-to-toe check after walks so you spot any issues early.

Treatment Options

The best way to tell whether the redness in your dog’s eyes is serious is to schedule an appointment with your veterinarian. They may perform tests to diagnose the cause of the redness. They’ll also check for dry eye and/or a corneal scratch or ulcer. Best of all, they’ll collect the information they need to prescribe treatment options which can come in a variety of forms. From antibiotics to topical ointments to anti-inflammatory medications, and even surgery in more serious cases, your vet should be well equipped to evaluate your dog’s case and help get them on their way to feeling more comfortable.

For more expert tips on dog eye problems, explore our other dog symptom articles. 

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