A subconjunctival hemorrhage is a small bleed that occurs beneath the conjunctiva, the thin transparent membrane covering the white of your eye. It looks alarming, often turning a large patch of the eye bright red seemingly overnight, but it is almost always harmless and clears on its own within one to two weeks. The condition is one of the most common causes of sudden eye redness, and while the appearance can send people rushing to an emergency room, it typically causes no pain and no change in vision.
What Actually Happens in Your Eye
The conjunctiva is laced with tiny, fragile blood vessels. When one of these vessels breaks, blood leaks into the space between the conjunctiva and the sclera (the tough white layer underneath). Because the conjunctiva is clear, the trapped blood is immediately visible as a vivid red patch. Unlike bloodshot eyes from irritation or allergies, where redness comes from dilated vessels, a subconjunctival hemorrhage produces a flat, uniform pool of blood that can cover part or all of the white of the eye.
The blood stays trapped in place. It does not spread into the eye itself, does not reach the iris or the retina, and does not affect how light enters your eye. That is why vision remains completely normal even when the hemorrhage looks dramatic. There is no pain, no light sensitivity, and no change in pupil size. These absent features are actually clinically useful because they help distinguish a subconjunctival hemorrhage from more serious conditions that do cause those symptoms.
Why It Happens
The causes split broadly by age. In younger people, the most common triggers are eye trauma and contact lens use. In older adults, underlying vascular diseases like hypertension, diabetes, and hardening of the arteries are more frequently involved.1PubMed Central. Subconjunctival hemorrhage: risk factors and potential indicators But a wide range of everyday events can rupture those delicate vessels in anyone:
- Sudden pressure spikes: Hard sneezing, violent coughing, vomiting, heavy lifting, or straining during a bowel movement can briefly spike venous pressure in the head and rupture a conjunctival vessel.
- Rubbing your eyes: Vigorous rubbing, especially when your eyes are dry or irritated, can be enough to break a small vessel.
- Minor trauma: A bump to the eye area, getting poked by a child’s finger, or even sleeping face-down on a pillow in an awkward position.
- Contact lenses: Both insertion and removal can cause microtrauma to the conjunctival surface.
Many people wake up with one and never identify a clear cause. That is normal. The vessel can break during sleep, during a mild cough you barely noticed, or seemingly for no reason at all.
The Hypertension Connection
High blood pressure deserves its own discussion because the link is well established and has practical implications for people who experience subconjunctival hemorrhages without an obvious mechanical trigger. A study comparing 78 patients with spontaneous subconjunctival hemorrhage to 78 controls found that blood pressure was significantly higher in the hemorrhage group. By World Health Organization criteria, 46% of the hemorrhage patients qualified as hypertensive at presentation, compared to 23% of controls.2PubMed Central. Spontaneous subconjunctival haemorrhage–a sign of hypertension? The researchers recommended that anyone presenting with a subconjunctival hemorrhage should have their blood pressure checked, as it may be the first visible clue that blood pressure is too high.
This does not mean every subconjunctival hemorrhage signals high blood pressure. Most are still caused by minor mechanical events. But if you keep getting them without an obvious cause, or if you have not had your blood pressure checked recently, the hemorrhage is worth treating as a prompt to visit your doctor. In one analysis of patients with spontaneous subconjunctival hemorrhage, hypertension was the most commonly associated systemic condition, found in about a quarter of cases.3PubMed Central. Analysis of subconjunctival hemorrhage
Blood Thinners and Bleeding Risk
If you take anticoagulants like warfarin or newer blood-thinning medications, you are understandably more concerned when blood appears anywhere on your body. Subconjunctival hemorrhages do occur in people on blood thinners, and the hemorrhages can look larger or more dramatic because the blood’s ability to clot is reduced. One study tracking warfarin patients found that when subconjunctival hemorrhage occurred, roughly three-quarters of those patients had their blood-thinning levels within the intended therapeutic range, meaning the hemorrhage happened even without excessive anticoagulation.4PubMed. Risk factors and complications of subconjunctival hemorrhages in patients taking warfarin About half of those patients had recently changed something in their medication regimen during the month before the bleed.
A case report of a particularly large subconjunctival hemorrhage in a patient on therapeutic warfarin noted that even when blood-thinning levels are technically in range, the degree of hemorrhage can be striking.5American Journal of Ophthalmology Case Reports. Massive spontaneous subconjunctival hemorrhage in a patient on therapeutic warfarin: A case report The good news from the warfarin study is that no eye-related complications resulted from any of the hemorrhages. The blood eventually reabsorbed just as it does in people not on blood thinners, though it may take somewhat longer. If you are on anticoagulants and develop a subconjunctival hemorrhage, you do not need to stop your medication, but let your prescribing doctor know, especially if the hemorrhage is unusually large or keeps recurring.
How Recovery Works
A subconjunctival hemorrhage follows a predictable course. It does not require treatment. The blood is gradually reabsorbed through the conjunctival lymphatic system, and most hemorrhages resolve fully within one to two weeks.6PubMed. Subconjunctival Hemorrhage The timeline depends on the size of the bleed, your age, and whether you have conditions that slow healing, like diabetes or poor circulation.
The color change during healing is worth knowing about so it does not catch you off guard. The patch starts bright red. Over a few days it deepens to a darker red or maroon. Then it transitions through yellowish-green shades as the trapped hemoglobin breaks down into its byproducts, the same process that gives a bruise on your skin its familiar rainbow progression. Just before it fully clears, the area may look faintly yellow. This color sequence is completely normal and actually a reassuring sign that reabsorption is on track.
There is nothing you need to do to speed up recovery. Artificial tears can help if the eye feels mildly scratchy, since the pooled blood can slightly raise the surface of the conjunctiva and make blinking feel a little different. Avoid rubbing the eye, which could re-injure the area or break additional vessels. Cold compresses in the first day or two might prevent the bleed from spreading slightly, and warm compresses after the first 48 hours may help encourage reabsorption, but neither will dramatically change the timeline.
When to Actually Worry
The overwhelming majority of subconjunctival hemorrhages are completely benign, but a few patterns warrant medical attention. A single episode with a clear mechanical trigger and no other symptoms almost never needs follow-up beyond perhaps a blood pressure check. The situations that do need attention include:
- Recurrent hemorrhages: Multiple episodes within a few months, especially without obvious causes, should prompt evaluation for underlying bleeding disorders, uncontrolled hypertension, or medication side effects.1PubMed Central. Subconjunctival hemorrhage: risk factors and potential indicators
- Pain or vision changes: A true subconjunctival hemorrhage causes neither. If you have eye pain, blurred vision, light sensitivity, or discharge along with the redness, something else may be going on.
- Trauma to the eye: If the hemorrhage followed a significant blow to the eye or face, the blood may be masking more serious damage underneath. An eye exam can rule out injury to deeper structures.
- Bleeding elsewhere: If you are also noticing easy bruising, nosebleeds, or bleeding gums, the subconjunctival hemorrhage may be part of a broader bleeding tendency that needs investigation.
For the straightforward single episode, though, the dramatic appearance truly is the worst part of it.
Subconjunctival Hemorrhage After Eye Surgery
If you have had or are planning eye surgery, particularly LASIK, you should know that subconjunctival hemorrhage is a common and expected side effect. The suction ring used during LASIK can compress conjunctival vessels, and the resulting hemorrhage can persist for days afterward. A study of LASIK patients found that about half of eyes in the control group developed subconjunctival hemorrhage either during or after the procedure. Interestingly, the same study tested whether applying brimonidine eye drops before surgery could reduce this, and it cut the rate from roughly 46–50% down to about 9%.7Scientific Electronic Library Online (SciELO) / Arquivos Brasileiros de Oftalmologia. Diluted brimonidine for improving early postoperative symptoms and subconjunctival hemorrhage after PRK and LASIK
Post-surgical subconjunctival hemorrhage resolves on its own just like the spontaneous kind. Surgeons typically warn patients in advance so the red eye does not cause panic during recovery. If you had any eye procedure and notice expanding redness, worsening pain, or new vision changes beyond what your surgeon described as expected, contact their office, but a stable red patch that slowly fades is normal healing.
A Loose Conjunctiva Can Make Things Worse
Some people seem especially prone to subconjunctival hemorrhages, and one structural reason involves a condition called conjunctivochalasis, where the conjunctiva becomes loose and redundant, forming folds on the surface of the eye. A study comparing over 100 patients with subconjunctival hemorrhage to age-matched controls found significantly more conjunctival looseness in the hemorrhage group across all areas of the eye.8Elsevier / Ophthalmology. Subconjunctival hemorrhage and conjunctivochalasis The number of areas involved by the hemorrhage correlated with the severity of the conjunctival loosening.
Conjunctivochalasis tends to develop with age as the conjunctival tissue loses elasticity. When this tissue is looser, it is more easily displaced during eye movements and blinking, which can put extra mechanical stress on the blood vessels running through it. This helps explain why older adults have more frequent subconjunctival hemorrhages even beyond the vascular risk factors like hypertension. If you are over 50 and keep getting these hemorrhages, the looseness of your conjunctival tissue may be a contributing factor worth discussing with an ophthalmologist, particularly if it is also causing a foreign-body sensation or tearing.
Newborns and Subconjunctival Hemorrhage
Parents sometimes notice a red patch on their newborn’s eye shortly after birth. This is more common than many people realize, especially after vaginal delivery, where the mechanical pressure of passing through the birth canal can rupture fragile conjunctival vessels. A study at a tertiary care hospital confirmed that subconjunctival hemorrhage was significantly more common in infants born vaginally compared to those delivered by cesarean section.9PubMed Central. Subconjunctival hemorrhage in the newborn: Experience of a tertiary care hospital The same study recommended that when subconjunctival hemorrhage is detected in a newborn, a fundus examination should be performed to rule out retinal hemorrhage, which can occasionally accompany it.
In newborns, as in adults, the hemorrhage itself is benign and resolves without treatment. But because the baby cannot report vision changes or discomfort, clinicians tend to be slightly more thorough in checking for associated findings. If your baby has a red patch on the eye after delivery, it is not an emergency, but it is worth pointing out to your pediatrician if the medical team has not already noted it.
Unusual Triggers You Might Not Expect
Beyond the common causes, a few less obvious triggers are documented. Breath-hold diving can cause subconjunctival hemorrhage through a form of barotrauma. As a diver descends, increasing water pressure compresses air-filled spaces in the body, and if pressure is not equalized properly, the resulting pressure differential can rupture conjunctival vessels.10PubMed Central. Preventable Diving-related Ocular Barotrauma: A Case Report Proper mask equalization technique prevents this.
Seasonal and age-related patterns have also been studied. Research examining over 160 patients with subconjunctival hemorrhage across different times of year has looked at whether certain seasons bring more cases, likely because conditions like colds and flu, which cause coughing and sneezing, cluster in winter months. Extremely vigorous exercise, particularly heavy weightlifting with breath-holding (the Valsalva maneuver), can spike head and neck venous pressure enough to cause a bleed. Even a particularly intense rollercoaster ride has been anecdotally linked to the condition in rare cases, though formal studies on that are understandably sparse.
Subconjunctival Hemorrhage in Dogs
Pet owners searching for information about red eyes may be looking at their dog, not themselves. Subconjunctival hemorrhage in dogs follows a different pattern than in humans. A study of 147 dogs with the condition found that the overwhelming majority, 119 out of 147, had a history of trauma, most commonly from being hit by a vehicle or attacked by another dog.11PubMed. Subconjunctival haemorrhage in 147 dogs Among the 28 dogs without a trauma history, the most common cause was a bleeding disorder, particularly immune-mediated thrombocytopenia, a condition where the immune system destroys the dog’s own platelets.
Unlike in humans, where a subconjunctival hemorrhage is overwhelmingly benign and can be safely watched at home, a red eye in a dog is more likely to signal a serious underlying problem and warrants a veterinary visit. Dogs also cannot tell you whether their vision has changed or whether they are in pain, so the “watch and wait” approach that works well for humans does not translate well to veterinary care.
What Not to Do
The most common mistake people make with subconjunctival hemorrhage is overreacting to the appearance. The second most common mistake is trying to treat it. Avoid aspirin or ibuprofen specifically for the hemorrhage, as these medications can inhibit platelet function and theoretically prolong the bleed (though if you take aspirin daily for heart protection, do not stop it over a subconjunctival hemorrhage without consulting your doctor). Do not use redness-relieving eye drops like those containing tetrahydrozoline. These work by constricting blood vessels to reduce the appearance of bloodshot eyes, but they have no meaningful effect on a pool of already-escaped blood sitting under the conjunctiva. They simply cannot address the problem, and using them repeatedly can cause rebound redness once you stop.
Wearing sunglasses can help if you are self-conscious about the appearance, and there is no shame in that. The eye can look genuinely startling, and fielding concerned questions from coworkers for a week gets old fast. Some people also find that the eye feels slightly drier or grittier than usual during the healing process, in which case preservative-free artificial tears a few times a day can help with comfort.