A dog’s eyes can appear red or bloodshot for many reasons—some of which are minor and will quickly resolve, and others which are much more serious.
Why Are My Dog’s Eyes Bloodshot?
General causes of red eyes in dogs include:
- Debris caught in the eye, such as grass or dust
- Scratch on the cornea
- Allergies
- Infection
- Corneal ulcer
- Entropion (eyelid folding inward) so that the eyelashes rub against the surface of the eye)
- Exhaustion
- Cancerous tumor inside or behind the eyeball
Having something caught in the eye causes irritation, and then your dog may make things worse by rubbing at the eye. Both the foreign object itself and your dog’s claws can potentially scratch the cornea. Entropion behaves similarly, except the eyelashes are a constant source of irritation that can’t be blinked or washed away.
Brachycephalic, flat-faced dogs have an increased risk of damage to the eyes. This is because their eyes typically stick out more than a “normal” dog’s would, making them more prominent and more vulnerable to being bumped.
Allergies cause irritation throughout the body, and this can be made worse if an allergen such as pollen gets in the eyes. Itchy eyes are no fun, and appear red both from inflammation and from chronic scratching and rubbing.
Bacterial infections typically only occur in the eye after it has been scratched, giving the bacteria a place to settle. These infections are very uncomfortable, and can also progress to corneal ulcers that eat through the cornea which can lead to rupture of the eyeball.
Other causes of bloodshot eyes are more predictable in appearance and show up in specific ways.
Bloodshot eyes in dogs will look different depending on what part of the eye is affected and the underlying cause. Here are the five primary ways that red eyes in dogs can manifest:
- Conjunctival hyperemia: red, puffy tissue around the eye or eyes, similar to pink eye in humans
- Corneal neovascularization: red lines (tiny blood vessels) stretching across the front of the eyeball where it should be clear
- Episcleral injection: red lines crisscrossing the white part of the eye
- Hyphema: solid red across the eye, blocking the iris and pupil
- Subconjunctival hemorrhage: white part of the eye is solid red
These details are a bit disturbing to think about, but they give clues as to why your dog’s eyes are red and help your veterinarian to determine necessary testing and treatment.
Conjunctival Hyperemia
Red tissues around the eyes, or conjunctivitis, usually indicates a problem on the outer surface of the eye or in the surrounding conjunctival tissue. This could occur when your dog has an infection that is irritating the eye, or when something like entropion or allergies are causing your dog to rub her eyes frequently.
One unique variation of conjunctival hyperemia is “cherry eye,” when your dog’s third eyelid gland becomes inflamed and pops out. If your dog is suffering from cherry eye, she will have a cherry-red blob at the inner corner of one or both eyes. This problem can occur in any dog, but is most common in brachycephalic, flat-faced dogs.
Corneal Neovascularization
Tiny red blood vessels growing across the surface of the cornea happens either because the cornea has been damaged and your dog’s body is trying to protect it, or due to an autoimmune disorder.
Scratches and ulcers on the cornea that are not treated can progress quickly. The best way for your dog to try to heal these injuries is to grow blood vessels to bring nutrients and immune cells to the area.
Keratoconjunctivitis sicca, known as KCS or “dry eye,” is an autoimmune disorder where the eye does not produce adequate tears to lubricate the eye. A dry cornea is at risk of damage, so your dog’s body responds by producing thick mucous and possibly growing blood vessels to patch the damaged areas.
Chronic superficial keratitis, or “pannus,” is an autoimmune disorder where blood vessels and/or pigment grows across the cornea for no good reason. Left untreated, pannus can progress to blindness.
Both dry eye and pannus require lifelong treatment, but can be managed successfully.
Episcleral Injection
Red lines across the white part of the eye typically indicates a problem inside the eye itself. Some causes include glaucoma, uveitis, or cancer.
Glaucoma is when blocked tear ducts leads to a buildup of pressure inside the eye. This hurts! As well as having red lines across the sclera, the eye may also appear bulgy. Left untreated, glaucoma will result in blindness.
Uveitis is inflammation of the tissues inside the eyeball. It can happen because of infection, traumatic injury, or an autoimmune disorder. Unlike glaucoma, uveitis can cause abnormally low eye pressures.
Cancer around the eye is uncommon, but tumors can form inside the eyeball itself or behind the eyeball within the socket. As the tumor grows, it puts pressure on the eye, becoming uncomfortable and possibly impairing vision.
Hyphema
A blood-filled eye is usually the result of trauma to the eye. For example, this can occur when a dog has been hit by a car. Hyphema can also occur because of high blood pressure, clotting disorders, or uveitis (inflammation inside the eye).
Subconjunctival Hemorrhage
If the white part of the eye is solid red, there has probably been trauma to the eye. Strangulation or excessive pressure on the neck and clotting disorders can also cause this to happen.
How to Treat Red Eyes in Dogs
Your veterinarian will start by looking at your dog’s eyes and doing some basic tests to measure tear production and eye pressure and check for corneal scratches and ulcers. She will also consider any other symptoms your dog is experiencing and her health history.
The most common causes of bloodshot eyes in dogs can be diagnosed and treated by your regular veterinarian. Debris, cherry eye, dry eye, pannus, glaucoma, and corneal ulcers are all usually easy to identify. Complicated cases or more obscure eye issues may require a trip to a veterinary ophthalmologist (specialist eye doctor).
Treatment varies depending on what is causing your dog’s red eyes. Many eye disorders are treated with medicated drops or ointments that are applied directly to the eye. Conjunctivitis due to allergies will require treatment for the allergies in general, and clotting disorders require specialized treatments.
Some eye problems, such as severe corneal ulcers, some cases of glaucoma, entropion, and cherry eye, may require surgery.
When to Get Help for Bloodshot Eyes in Dogs
Eye problems can progress very quickly and threaten your dog’s sight. Because of this, we recommend making a vet appointment as quickly as possible if your dog’s eyes appear abnormal or she is scratching and rubbing at them. Squinting is also a cause for concern.
If your dog is in pain, she may need emergency care.
Don’t try to treat your dog’s bloodshot eyes on your own. Very few medications are safe to put in the eyes, and using the wrong eye medication (for example, steroid drops when the dog actually has an ulcer) can make the situation worse.
One thing that you can do to help your dog while waiting for a vet appointment is apply plain artificial tears. I really like the GenTeal Tears Severe Lubricant Eye Gel, which was recommended to me by a veterinary ophthalmologist. The gel lasts longer than typical artificial tears, providing extra relief for your dog.
Artificial tears won’t treat most eye problems but do provide soothing lubrication and can flush out debris in the eye.
