Dogs express themselves through their eyes. Whether they are begging for table scraps, anticipating you tossing the ball, or asking forgiveness for a torn-up sock, dogs’ big eyes make them hard to ignore. That’s why when there is something wrong with your dog’s eyes, you take notice. 

According to most veterinarians, eye problems are emergencies because they can quickly progress. Any eye issue allowed to continue can eventually cause blindness, but before then is likely to cause your pup pain. 

By understanding what causes red eyes in dogs and other eye-related symptoms, you can get your pet the help she needs. 

Appearance of Red Eyes 

A dog’s eyes can appear red when one or more parts of the eye are irritated. The conjunctiva is the soft tissue around a dog’s eye but inside the eyelid. The sclera is normally the white part of the eye. The cornea is the covering of the globe itself and is usually clear. 

More rarely, diseases of the whole body allow red blood cells to accumulate in the space in front of the iris. Redness in each of these different structures of the eye has different causes.

Causes of Red Eyes in Dogs

There are many causes of red eyes in dogs, ranging from allergies and infections to severe trauma and disease. 

Some breeds and types of dogs are more prone to eye redness. A long nose helps protect a dog’s eyes from debris and objects. As such, flat-faced (brachycephalic) dogs are more likely than other breeds to have red eyes and other eye issues. Dogs with long hair are also prone to red eyes because hair touching the eye is irritating. 

Older dogs with illnesses, including diabetes and kidney disease, may develop red eyes associated with disease symptoms.

Here’s a closer look at some of the causes of red eyes in dogs:

Allergies: Just like in humans, allergies can cause red eyes in dogs. Allergies usually cause redness of both eyes, although one may look more red than the other. 

Trauma: Trauma usually affects only one eye and refers to physical harm to the eye. It includes scratches from a wayward branch, a cat’s claw, or a dog’s own hair. Severe trauma such as being hit by a car can also cause red eye due to hemorrhage. Trauma can also occur if microscopic bits of debris accumulate on the eye, as may occur in dogs with sagging lower eyelids.

Infection: Conjunctivitis, an infection of the conjunctiva (tissue inside the eyelids), is known as “pink eye” because the eye looks red and puffy. It is uncomfortable and causes dogs to rub their eyes, worsening the redness.

Ulcers: Corneal ulcers, or damage to the protective covering of the eye, is a cause of red eye that needs to be treated by a veterinarian immediately. Usually only one eye is affected.

Dry Eye: When the tear-producing glands around the eye do not produce enough tears, this dries out the eye, which leads to redness. This is also known as keratoconjunctivitis sicca (KCS) and is common in brachycephalic dogs. Usually both eyes are affected, though one may be more severe than the other.

Glaucoma: Glaucoma is when the pressure inside of the eye itself (intraocular pressure) gets too high. This is a painful medical emergency. One or both eyes may be affected. 

“Cherry Eye”: Cherry eye is the term used to describe when the third eyelid of a dog is elevated and swollen or puffy. It is most common in brachycephalic breeds due to a genetic weakness of the ligament that keeps the eyelid in place. 

Other diseases that affect the whole body, including some viruses and diseases acquired from ticks, may cause red eyes in dogs. Rarely, cancer can cause redness of the eyes as well.

Symptoms that Accompany Red Eyes in Dogs

If your dog’s eyes are red, she may also have other eye-related symptoms that can help you and your veterinarian diagnose the specific cause. If your dog has any other full-body symptoms, such as lethargy, not eating, or bleeding anywhere else, she needs to be seen by a veterinarian immediately. 

Dogs often have combinations of eye symptoms that include redness. The specific symptoms will help your veterinarian diagnose the reason your dog’s eyes are red.

Squinting: If your dog is squinting, she needs to be seen by a veterinarian right away. This is a sign of pain and can indicate a severe problem.

Rubbing: A dog rubbing her eyes is a sign of pain or itchiness. Rubbing or scratching at her eyes can make the problem worse or cause damage to the eye.

Discharge: Eye discharge can be watery, thick with mucus, or be purulent (infectious). Discharge can be associated with many causes of red eye.

Swelling: Infection or irritation can cause swelling of the tissue around the eye or a puffy appearance. If the eye itself looks swollen and bulging, that is a medical emergency and needs to be treated by a veterinarian right away.

Cloudy or Opaque: If your dog’s pupil is suddenly hidden behind a cornea that is cloudy or opaque, that is a sign of corneal damage that needs to be addressed immediately by your veterinarian. Occasionally, animals will have an injury that leaves opaque scar tissue on the eye. This scar tissue is not painful but does inhibit vision.

Diagnosing Red Eyes in Dogs

Your veterinarian will first perform a complete physical exam. The physical exam is important in determining if there are any other signs or symptoms associated with the eye redness and help in an accurate diagnosis. 

Next, your veterinarian will examine your dog’s eye with an ophthalmoscope, a tool that allows her to look at the different structures of the eye. Depending on the specific symptoms your dog is showing, your veterinarian may perform one or more of the following tests:

• Schirmer Tear Test: If your veterinarian thinks your pet may not be producing adequate tears, this test is used. 
• Tonometry: This tests the pressure of the eye. Both high and low pressures are indications that something is wrong. High eye pressure (intraocular pressure) often requires emergency treatment. 
• Fluorescein Stain: Your veterinarian uses this special dye to detect small defects in the cornea, known as corneal ulcers. The presence or absence of an ulcer determines which type(s) of medications are appropriate for your dog. 

In addition, your veterinarian may recommend blood tests. Some illnesses, including kidney disease, diabetes, and those transmitted by ticks, can cause problems that lead to red eyes in dogs. Rarely, cancer can also cause red eyes, therefore your veterinarian may recommend X-rays and/or an ultrasound to look for spread of the cancer. 

For complicated or severe cases of eye disease, your veterinarian may refer you to a veterinary ophthalmologist. These are veterinary specialists who have additional tools and training to take care of your dog’s eyes.

How to Treat Red Eye in Dogs

Proper treatment depends on the cause of eye redness. Your veterinarian may prescribe topical (applied to the eye) or oral (taken by mouth) medications to treat your dog’s red eyes. Some corneal ulcers may require minor procedures in the clinic while glaucoma and cherry eye often require surgery to treat.

Red Eye Medication for Dogs

For eye irritation and infection, your veterinarian will prescribe an ointment with antibiotics and possibly steroids. Steroids are never appropriate when there is an open corneal ulcer. Your veterinarian may also prescribe pain relieving topical medication, medication to reduce intraocular pressure, or other medicine as appropriate.

Always give medication as directed and for as long as prescribed. Follow-up with your veterinarian as recommended. 

If your veterinarian recommends topical eye medicine, they can be challenging to apply to some dogs. Ask your veterinarian for advice. 

How to Treat Your Dog’s Red Eyes at Home

Red eye in dogs can be treated at home if you know the cause of the redness and your veterinarian has recommended at-home care. For example, if you know your dog has allergies, then giving an antihistamine according to veterinary instructions can help reduce her symptoms. 

Keep your dog’s eyes clean so that discharge can’t accumulate and worsen irritation. Never scrub around your dog’s eyes but rather allow a clean, damp, warm washcloth to moisten the debris over 30-60 seconds so that debris wipes away without pressure.  

Eye problems can be an emergency so call your veterinarian before attempting any at-home treatment. Never attempt any care without consulting with your veterinarian.

Cost of Red Eye Treatment in Dogs

Most causes of red eye can be treated without breaking the bank. However, due to the many causes of red eye, it is impossible to predict the cost ahead of time. 

Irritation due to allergies or conjunctivitis may only cost a veterinary visit plus topical medicine (approximately $100 total) but cherry eye or glaucoma may need to be treated with surgery estimated at $1,000-$4,000.

In the middle, corneal ulcers can require multiple types of medication and visits to your veterinarian, costing $200-$500 or more. 

In general, the sooner you bring your dog to be seen, treatment is easier and therefore less costly.

How to Prevent Red Eyes in Dogs

Unfortunately, there is not much you can do to prevent red eyes in dogs. If your dog has allergies, keeping the house clean and dust-free can help reduce symptoms, including red eyes.  

Dogs with dry eye (KCS) should be given their medication on schedule. For other conditions, following your veterinarian’s treatment instructions are the best way to prevent red eyes from returning.

Red eyes in dogs don’t cause many other problems but they can be a sign of many different illnesses. As they say, “the eyes are the window to the soul,” and in dogs they are also a window into the health of the body.

Related Conditions

• Conjunctivitis (Pink Eye)
• Keratoconjunctivitis Sicca (KCS)
• Corneal Ulcer
• Glaucoma
• Cherry Eye