The short answer
Red eyes in dogs are most often caused by conjunctivitis (inflammation of the pink lining around the eye from allergies, irritation or infection), which is uncomfortable but rarely urgent. A red eye that is painful, with squinting, holding the eye shut, a cloudy or bluish surface, a bulging eye or sudden vision problems, is different: corneal ulcers, uveitis and glaucoma can damage sight quickly and need a vet the same day.
Call a vet now if your dog has
- Squinting, holding the eye shut, or pawing and rubbing at the eye
- The eye suddenly looks cloudy, blue-grey or hazy
- The eye looks bigger, bulges, or the pupils are different sizes
- Bumping into things or other sudden changes in vision
- An injury to the eye, or anything stuck in it
- Red eye after contact with a chemical, cleaning product or plant sap
When owners say their dog’s eyes look red, they can mean several different things: pink, puffy skin around the eye, a reddened white of the eye, a red lump in the corner, or the whole eye looking bloodshot. The causes range from a bit of pollen to conditions that can cost a dog its sight within a day or two.
The good news is that the most important distinction (painful or not painful) is something you can usually see at home.
The key question: is the eye painful?
Eyes are very sensitive, and dogs show eye pain in recognisable ways:
- squinting, or holding one eye partly or fully closed
- blinking a lot
- rubbing the face on the floor or furniture, or pawing at the eye
- a lot of watery tears from one eye
- avoiding bright light
- being head-shy or reluctant to be touched around the face
A red eye with any of these signs needs a vet the same day. Painful red eyes are where the sight-threatening conditions live. A red eye without pain, in a dog that is opening both eyes normally, is much more likely to be conjunctivitis or allergies and is usually less urgent, but should still be checked within a day or two if it does not settle.
Common causes of red eyes in dogs
Conjunctivitis, often called pink eye. The conjunctiva is the pink tissue lining the eyelids and covering the white of the eye. When it is inflamed, it looks red and swollen and the eye often produces discharge, clear and watery, or thicker and yellow-green. Causes include allergies, dust, smoke and other irritants, bacterial and viral infections, and problems with the eyelids or lashes rubbing on the eye.
Allergies. Seasonal or environmental allergies often cause red, itchy, watery eyes on both sides, usually alongside itchy skin, licking the paws or ear infections.
Dry eye (keratoconjunctivitis sicca). When the eye does not make enough tears, it becomes red, dull and irritated, with thick, sticky, yellow-green discharge. It is common in breeds such as Cocker Spaniels, West Highland White Terriers, Shih Tzus and Bulldogs, and usually needs lifelong eye medication to control.
Corneal ulcers. A scratch or erosion on the clear front surface of the eye is very painful. Dogs squint, water and rub at the eye. Ulcers can deepen quickly, especially in flat-faced breeds with prominent eyes, and need prompt treatment.
Uveitis. Inflammation inside the eye causes intense redness, pain, squinting, sensitivity to light and often a cloudy look. It can be linked to infections, immune disease or other illness elsewhere in the body, so your vet may also look for an underlying cause.
Glaucoma. Raised pressure inside the eye makes it red, painful, cloudy or blue-tinged, sometimes enlarged, with a dilated pupil. Acute glaucoma is a true emergency: vision can be lost within hours to days.
Cherry eye. A smooth red lump in the inner corner is usually the gland of the third eyelid popping out of place. It is not an emergency but does need a vet.
Injuries and foreign bodies. Scratches from plants or other animals, grass seeds caught behind the eyelids and chemical splashes all cause sudden redness and pain.
Dogs more prone to eye problems
Some dogs need a lower threshold for getting a red eye checked. Flat-faced breeds such as Pugs, Shih Tzus, French Bulldogs and Boston Terriers have prominent eyes that are more easily scratched and dry out more readily, so ulcers can develop and worsen quickly. Breeds with loose or rolled-in eyelids, such as Bloodhounds, Shar-Peis and some spaniels, are prone to irritation from lashes and lids. Older dogs and dogs with diabetes or other long-term illnesses are also more likely to have eye complications.
When to see a vet
| What you see | What to do |
|---|---|
| Mild redness, both eyes open normally, clear tears | Call your vet if it has not improved in a day or two |
| Red eyes with itchy skin or paws, no pain | Book a vet visit |
| Thick yellow or green discharge | See a vet within a day or two |
| Red lump in the inner corner | Book a vet visit |
| Squinting, rubbing, eye held shut | Same day |
| Cloudy, blue, bulging eye, or sudden vision loss | Same day, emergency |
| Chemical in the eye | Rinse with plenty of water, then go to a vet now |
What you can safely do at home
- Gently clean away discharge with a clean, damp cloth or cotton pad, using a fresh one for each eye and wiping away from the eye.
- Rinse with sterile saline if dust or debris is the likely cause. If anything chemical got into the eye, rinse it with plenty of lukewarm water for several minutes and go to a vet.
- Stop rubbing: a cone or soft collar can prevent your dog from making an ulcer worse while you wait to be seen.
- Keep the face clean and fur trimmed around the eyes in long-haired breeds.
Do not use leftover eye medicines from another pet or a previous problem, and do not use human redness-relieving or steroid drops. Some eye medicines are safe for conjunctivitis but can turn a small corneal ulcer into a serious one.
One painful eye is never “just conjunctivitis” until a vet says so
Ulcers, uveitis and glaucoma usually affect one eye and start out looking like a simple red eye. A vet uses a special stain and a pressure measurement to tell them apart, tests that only take a few minutes and can save the eye.
What the vet will do
Your vet will examine the eyes with a light and magnifier and will often perform a few quick tests: a fluorescein stain that makes corneal ulcers glow green, a tear test to check for dry eye, and a measurement of the pressure inside the eye to check for glaucoma and uveitis. Depending on the findings, treatment might include medicated eye drops or ointments, pain relief, treatment for allergies or an underlying illness, or referral to a veterinary ophthalmologist.
Related problems
Eye discharge and ear trouble often go together in allergic dogs. See how to clean your dog’s ears. If your dog has red, watery eyes along with a cough and sneezing after mixing with other dogs, read kennel cough symptoms. For more eye and ear guides, visit our ears and eyes section.
Common questions
Can I use human eye drops on my dog’s red eye?
Only plain sterile saline, to rinse away dust or debris. Redness-relieving drops and anything containing steroids or other medicines can make some eye problems (corneal ulcers in particular) dramatically worse. A vet needs to check the surface of the eye before anything medicated is used.
Can allergies make a dog’s eyes red?
Yes. Seasonal and environmental allergies commonly cause red, itchy, watery eyes, often alongside itchy skin, paw licking or ear problems. Allergic conjunctivitis is not usually urgent, but a vet should confirm the diagnosis, because more serious eye conditions can look similar at first.
Is a red eye in a dog contagious?
Most red eyes are not contagious. Allergies, dry eye, injuries and glaucoma cannot spread. Some infectious causes of conjunctivitis, such as certain viruses involved in kennel cough, can pass between dogs, so keep a dog with discharge and sneezing away from other dogs until it has been checked.
What is the red lump in the corner of my dog’s eye?
A smooth, red, rounded lump in the inner corner of the eye is usually cherry eye, a gland of the third eyelid that has slipped out of place. It is most common in young dogs of breeds such as Bulldogs, Beagles and Cocker Spaniels. It is not an emergency, but it needs a vet, and it is usually treated with surgery to put the gland back.
Sources
- Conjunctivitis in Dogs, VCA Animal Hospitals
- Uveitis in Dogs, VCA Animal Hospitals
- Corneal Ulcers in Dogs, VCA Animal Hospitals
- Dry Eye (Keratoconjunctivitis sicca), American College of Veterinary Ophthalmologists
This article is general information to help you decide what to do next. It is not a diagnosis and is not a substitute for examination by a veterinarian. If you are worried about your dog, call your vet.
Reviewed by Winzah, Editor, on . How we research and check articles.
