A subconjunctival haemorrhage in a dog is a patch of blood trapped under the clear membrane (the conjunctiva) that covers the white of the eye. It appears as a bright or dark red smear on the white, sometimes covering the whole surface. After a known knock to the head it can be minor. With no obvious cause, it can be the first visible sign of a clotting problem, high blood pressure or poisoning, so seeing your vet the same day is the safe default. To put those observations in context, see Ectropion in Dogs and Pannus in Dogs UK for related questions about eye care and changes to watch for. If suitability is your main concern, read Saline Solution for Dogs' Eyes before making a change.
If you’re comparing approaches to eye care and changes to look out for, see How to Get Something Out of My Dog's Eye, Red Eyes in Dogs and Dry Eye in Dogs. Read Watery Eyes in Dogs for more detail on eye care and changes to look out for.
What a subconjunctival haemorrhage looks like
The blood sits behind the clear membrane, so it cannot be wiped or rinsed away. It looks like a flat, sharply bordered red or burgundy patch on the sclera (the white). Ordinary eye redness is different: a diffuse pink-red flush from many tiny, enlarged vessels. If you are unsure which you are seeing, our guide to red eyes in dogs shows how the two differ.
If you’re comparing approaches to eye care and changes to look out for, see How to Clean Around a Dog's Eyes, Dog Ear and Eye Cleaners and Best Tear Stain Remover for Dogs. Our guide Pekingese Dog Care covers a related part of eye care and changes to look out for.
The Merck Veterinary Manual describes ruptured vessels under the conjunctiva as the result of trauma, a blood disorder or certain infectious diseases. It notes that the bleed alone does not need treatment, but the dog must be examined to find out why it happened and whether anything deeper inside the eye is involved.
To compare the signs and questions to take into account, see Dog Eye Stye and Uveitis in Dogs UK.
Common causes of subconjunctival haemorrhage in dogs
| Possible cause | Clues you may notice | How quickly to act |
|---|---|---|
| Head or eye trauma (a collision, rough play, a swipe from a cat or another dog) | Known bump, a single patch, dog otherwise bright and comfortable | Same-day vet check to rule out injury inside the eye |
| Anticoagulant rodenticide (rat bait) exposure | Bleeding with no injury, swollen or painful eye, bruising, bleeding gums, lethargy, possible access to bait | Emergency: phone your vet or out-of-hours clinic immediately |
| Low platelets or other clotting disorders | Bruises on the belly or gums, nosebleeds, dark stool, pinpoint red spots on the skin | Emergency or same day |
| High blood pressure (systemic hypertension) | Older dog, kidney or hormonal disease, sudden vision changes, blood inside the eye | Same day: vision can be at risk |
| Infectious or inflammatory disease | Fever, low energy, other bleeding, red eye with squinting | Prompt exam and blood tests |
The evidence behind the less obvious causes is real. In a review of 65 dogs, Leblanc and colleagues (JAVMA, 2011) found that 62% of hypertensive dogs (26 of 42) had at least one eye lesion, with retinal haemorrhage the most common at 40%. A Veterinary Ophthalmology case series (2016) described six dogs with mainly eye signs from anticoagulant rodenticide, including subconjunctival haemorrhage; every dog tested had a prolonged clotting time. A Canadian Veterinary Journal case (2023) reported a young dog whose scleral bleeding was the clue that led to the right diagnosis after the first guess was wrong. To work the relevant checks into your usual routine, see Dog Eye Cleaner.
For related questions about eye care and changes to look out for, read Bacterial Eye Infection in a Dog, Cherry Eye in Dogs and Blocked Tear Duct in Dogs.
When a red patch on your dog's eye is an emergency
Phone your vet or an emergency clinic straight away if the patch comes with any of the following:
- Any chance your dog ate rat or mouse bait, or you cannot account for where they have been
- Bleeding or bruising elsewhere: gums, nose, skin, urine or stool
- Squinting, a bulging eye, a cloudy cornea or an eye your dog will not let you touch
- A pupil that is a different size from the other, or blood visible inside the front chamber of the eye
- Sudden bumping into furniture, stumbling or other signs of vision loss
- Weakness, pale gums, collapse, laboured breathing or neurological signs
If your own practice is closed, ring its out-of-hours number: most UK practices either run an emergency service or direct you to a 24-hour clinic in the nearest large town or city, such as London, Manchester or Glasgow. If you hold pet insurance, check the policy for eye and emergency cover, but do not delay the visit while you do. For practical steps you can use when planning everyday care, see Best Dog Eye Cleaner for Tear Stains. To see what an estimate or purchase may include, use the examples in How Much Is a Vet Visit? 2026 Dog Vet Costs From Real Price Lists.
For more detail on eye care and changes to look out for, start with Dog Eye Health, Dog Eye Infection and The Origins of Veterinary Clinical Nutrition. For more on eye care and changes to look out for, see Dog Third Eyelid Showing.
Eye pain, a hazy cornea or pressure changes can point to conditions such as glaucoma in dogs or uveitis in dogs, which can steal sight in days. In older dogs, bleeding inside the eye of retinal origin carries a guarded outlook: in a North Carolina State series of 17 dogs with hyphaema (blood inside the eye) from retinal disease, 10 developed secondary glaucoma and all lost vision (Nelms et al., JAVMA, 1993). That is why a red eye should never be left to "see how it goes". If you’re trying to describe what you’ve noticed, Glaucoma in Dogs in the UK and Entropion in Dogs explain what to look for. Our guide to angel eyes for dogs explains this part of the topic in more detail.
To compare the signs and questions to take into account, see Dog Pink Eye and Cloudy Dog Eyes. For more detail on eye care and changes to look out for, start with Dog Eye Boogers, Dog Squinting One Eye and Dog Eye Allergy or Infection? Why an Examination Matters.
What your vet will check
Expect a full eye exam with fluorescein stain to look for a scratch (see dog eye ulcer), eye pressure measurement, and a look at the retina. Because spontaneous bleeding is a whole-body question, vets commonly add blood pressure, a clotting profile (PT and PTT), a platelet count and blood tests. A dog with an obvious, witnessed knock and a normal exam may need only monitoring, and your vet may refer you to a veterinary ophthalmologist if the inside of the eye is involved. Our dog eye infection guide explains how vets sort out redness, discharge and pain so you know what the appointment involves. If you’re reviewing what you may pay, Dog Cataract Surgery Cost UK and Optixcare Eye Lube for Dogs show which details are worth checking.
For related questions about eye care and changes to look out for, read Dog Eye Twitching and Can Dogs See Color? What Blue, Yellow, Red and Green Look Like.
What you can do at home, and what to leave alone
- Do not apply anything to the bleed. No human redness-relief drops, no home remedies, no massage. Nothing you put on the eye shortens a haemorrhage.
- Stop your dog from rubbing. A buster collar or soft cone protects the eye on the way to the vet.
- Take photos. A clear daily photo in natural light helps your vet judge whether the patch is fading or spreading.
- Note the timeline. When it appeared, any recent trauma, medication, bait or tick exposure.
- Keep the surrounding area clean once your vet has ruled out anything serious. Dried discharge and dust around the lids irritate the surface. A sterile, pH-matched dog eye cleaner is designed for that job: Pure Majesty Pets Dog Eye Drops are buffered to pH 7.0–7.2 to match canine tears, filtered sterile to 10 microns, and contain 0.05% sodium hyaluronate, 2% chamomile and 8% aloe, with no bleach, alcohol or fragrance. Many over-the-counter stain removers are acidic or bleach-based, which is the opposite of what a sore eye needs. It is a non-medicated hygiene product: it does not treat bleeding or any eye disease, and it ships free worldwide, including to the UK.
How long does a subconjunctival haemorrhage take to clear?
A small, uncomplicated patch usually fades gradually over days to a couple of weeks, changing colour from bright red toward darker red and then yellowish, much as a bruise does. Your vet can give you a timeframe for your dog. If the patch grows, new ones appear, or other signs develop, call back rather than waiting.
Frequently asked questions
Is a subconjunctival haemorrhage in a dog painful?
The bleed itself is usually not painful. Pain, squinting or a cloudy eye suggests a deeper problem such as a corneal injury or raised eye pressure and needs prompt care.
For more on eye care and changes to look out for, see Dog Corneal Ulcer.
Can a subconjunctival haemorrhage heal on its own?
Often the blood is gradually reabsorbed. The Merck Veterinary Manual notes the bleed itself does not require therapy, but the cause must be identified, so the eye should still be examined.
Read Dog Blinking: Eyelids, Tears and Everyday Eye Comfort for more detail on eye care and changes to look out for.
Can rat poison cause a bloody eye in dogs?
Yes. Anticoagulant rodenticides prevent normal clotting and have been reported to cause eye and orbital bleeding in dogs, sometimes with few other signs. If poisoning is possible, treat it as an emergency. For more detail on eye care and changes to watch for, see Over-the-Counter Eye Drops for Dogs.
For more on eye care and changes to look out for, see Swollen Eye in a Dog.
Can I use eye drops on a bleeding eye?
Do not put anything on the eye until a vet has examined it. Once cleared, a sterile, non-medicated rinse can be used around the lids for hygiene, but it will not treat the haemorrhage.
For more on eye care and changes to look out for, see Dog Eye Wipes. For more on eye care and changes to look out for, see Green Eye Discharge in Dogs.
Scientific References
- Gelatt KN. Disorders of the Conjunctiva in Dogs. Merck Veterinary Manual, pet owner version (updated September 2024). merckvetmanual.com
- Leblanc NL, Stepien RL, Bentley E. Ocular lesions associated with systemic hypertension in dogs: 65 cases (2005–2007). J Am Vet Med Assoc. 2011;238(7):915-921. doi:10.2460/javma.238.7.915. PMID 21453181
- Griggs AN, Allbaugh RA, Tofflemire KL, et al. Anticoagulant rodenticide toxicity in six dogs presenting for ocular disease. Vet Ophthalmol. 2016;19(1):73-80. doi:10.1111/vop.12267. PMID 25800104
- Brei C, Stern L, Racette M. An atypical presentation of anticoagulant rodenticide toxicosis in a dog. Can Vet J. 2023;64(11):1015-1020. PMID 37915786
- Nelms SR, Nasisse MP, Davidson MG, Kirschner SE. Hyphema associated with retinal disease in dogs: 17 cases (1986–1991). J Am Vet Med Assoc. 1993;202(8):1289-1292. PMID 8496090
Veterinary disclaimer: This article is educational and is not a substitute for veterinary diagnosis or treatment. A red patch on your dog's eye can signal a serious condition. Contact your vet or an emergency clinic promptly, and never give your dog medication without professional advice. More eye care guidance is on the Pure Majesty Pets homepage.