SymptomEyes & vision
Red Eye: Common Causes and When It Is Serious
A red eye happens when blood vessels on the surface of the eye widen or bleed. Most red eyes are caused by conjunctivitis (pink eye), dry eye, allergies, eyelid inflammation or a harmless burst blood vessel, and they settle with simple care. A red eye with significant pain, blurred vision, light sensitivity, a halo around lights, or after an injury or chemical splash can be sight-threatening and needs same-day eye care.
Also called: Bloodshot eye, pink eye, eye redness, injected eye
At a glance
- What it is
- Redness of the white of the eye from widened or burst blood vessels.
- Common causes
- Conjunctivitis, dry eye, allergies, blepharitis, subconjunctival hemorrhage, contact lens irritation.
- Serious causes
- Acute glaucoma, uveitis, keratitis and corneal ulcers, scleritis, injuries and chemical burns.
- Warning signs
- Pain, reduced vision, light sensitivity, halos, a hazy cornea, or an injury.
- Treatment
- Depends on cause: cool compresses, lubricating drops, antihistamines, antibiotics, or urgent specialist care.
When to get help
Call 911 or go to the ER
- A chemical splash in the eye: rinse with clean running water for at least 15 to 20 minutes, then go to an ER
- A red, painful eye with blurred vision, halos around lights, headache and nausea or vomiting (possible acute angle-closure glaucoma)
- A penetrating injury, a high-speed fragment from hammering or grinding, or a misshapen pupil after injury
- A red, swollen eyelid and eye with fever, pain on moving the eye or bulging eye
See a doctor within a day or two
- A red eye with moderate to severe pain, light sensitivity or reduced vision
- A contact lens wearer with a red, painful eye (possible corneal ulcer); remove the lens and do not wear it again until checked
- A white spot on the clear front of the eye (cornea)
- Redness concentrated in a ring around the colored part of the eye
- Deep, boring eye pain that wakes you at night (possible scleritis)
- A newborn under 4 weeks with red, sticky eyes
- Shingles rash on the forehead or tip of the nose with a red eye
Book a routine appointment
- Red eye not improving after 1 week of home care
- Recurring red eyes, or a red eye with joint pain or back stiffness
- Repeated burst blood vessels, especially if you take blood thinners or have high blood pressure
Usually safe to manage at home
- A bright red patch on the white of the eye with no pain or vision change (burst blood vessel)
- Red, itchy, watery eyes in allergy season
- Gritty, mildly red eyes after screen work, wind or air conditioning
- Red eyes with sticky discharge but normal vision and only mild discomfort
Common causes of a red eye
Conjunctivitis (pink eye)
Inflammation of the thin membrane covering the white of the eye and the inside of the lids. See conjunctivitis.
- Viral: watery discharge, gritty feeling, often starts in one eye and spreads to the other, often with a cold. Very contagious; lasts 1 to 3 weeks.
- Bacterial: thick yellow or green discharge, lids stuck together in the morning. Often clears in a week; antibiotic drops speed recovery.
- Allergic: both eyes, intense itching, watery discharge, puffy lids, with hay fever or after contact with pets.
Subconjunctival hemorrhage
A bright red, flat patch on the white of the eye from a burst blood vessel, often noticed in the mirror. It is painless and does not affect vision. Coughing, sneezing, straining, rubbing the eye or blood thinners can cause it. It clears in 1 to 3 weeks, changing color like a bruise. See subconjunctival hemorrhage.
Dry eye
Not enough tears or poor-quality tears cause redness, grittiness, burning and paradoxically watery eyes, worse with screens, wind, air conditioning and contact lenses. See dry eye.
Blepharitis
Inflammation of the eyelid margins with crusting, itching and red lid edges, often with dandruff or rosacea. It is long-term but controlled with daily lid hygiene. See blepharitis.
Other common causes
- contact lens overwear or poor lens hygiene
- irritants: smoke, chlorine, makeup
- a small foreign body or scratch (corneal abrasion), causing pain, watering and light sensitivity
- alcohol, cannabis, lack of sleep
- episcleritis: a sectoral patch of redness with mild discomfort, usually harmless
Serious causes of a red eye
| Condition | Key features |
|---|---|
| Acute angle-closure glaucoma | Severe eye pain, headache, blurred vision, halos, nausea, a mid-dilated pupil, a hazy cornea |
| Uveitis (iritis) | Aching pain, light sensitivity, redness around the colored part, blurred vision; linked to ankylosing spondylitis and IBD |
| Keratitis and corneal ulcer | Pain, light sensitivity, reduced vision, white spot; contact lens wearers at high risk |
| Scleritis | Severe, deep, boring pain, tender eye, purple-red color; linked to rheumatoid arthritis |
| Herpes eye disease | Pain, light sensitivity, often one eye, past cold sores or shingles on the face |
| Chemical injury | Immediate pain after a splash, especially alkalis such as lime, cement and drain cleaner |
| Orbital cellulitis | Swollen red lids, fever, painful eye movements, bulging eye |
Telling causes apart
| Clue | Points toward |
|---|---|
| Itching | Allergy |
| Sticky yellow discharge | Bacterial conjunctivitis |
| Watery discharge with a cold | Viral conjunctivitis |
| Painless, sharply defined red patch | Subconjunctival hemorrhage |
| Pain and light sensitivity | Uveitis, keratitis, abrasion |
| Reduced vision | Serious cause until proven otherwise |
| Halos and vomiting | Acute glaucoma |
How a red eye is diagnosed
An optometrist, primary care doctor or ophthalmologist will check your vision first, then examine the lids, the pattern of redness, the cornea and the pupil, often with a slit lamp. Fluorescein dye shows scratches and ulcers under blue light. Eye pressure is measured if glaucoma is possible. Swabs are taken for severe or newborn infections and contact lens ulcers.
Treatment and home care
- Cool compresses reduce redness and itching.
- Lubricating eye drops (artificial tears) ease dry eye and irritation; preservative-free drops are better for frequent use.
- Antihistamine eye drops such as ketotifen relieve allergic conjunctivitis.
- Warm compresses and lid cleaning for blepharitis, once or twice daily.
- Antibiotic drops for bacterial conjunctivitis or corneal infection, prescribed by a clinician.
- Steroid or other specialist drops for uveitis, prescribed and monitored by an eye doctor only.
- Stop wearing contact lenses until the eye is completely better.
- Avoid "redness-relief" drops with vasoconstrictors for more than a few days; they can cause rebound redness.
Preventing spread of conjunctivitis
Wash hands often, avoid touching your eyes, use your own towel and pillowcase, and do not share eye makeup. Children can usually go to school unless they feel unwell, depending on local policy.
Frequently asked questions
What causes a red eye?
The most common causes are conjunctivitis (viral, bacterial or allergic), dry eye, blepharitis, a burst blood vessel, and irritation from contact lenses, smoke or tiredness. Less common but serious causes include acute glaucoma, uveitis, corneal infections and eye injuries.
When is a red eye an emergency?
Get urgent care for a red eye with significant pain, blurred vision, light sensitivity, halos around lights, nausea, a white spot on the cornea, an injury or chemical splash, or a red eye in a contact lens wearer. These can threaten sight.
Is a red eye without pain serious?
Usually not. A painless bright red patch is most often a burst blood vessel, which clears in 1 to 3 weeks. Painless redness with discharge is usually conjunctivitis. However, see a doctor if vision changes or redness persists beyond a week.
Should I see a doctor for pink eye?
Many cases of pink eye settle on their own within 1 to 2 weeks. See a doctor if there is pain, light sensitivity, blurred vision, a thick discharge that does not improve, if you wear contact lenses, or if a newborn has red, sticky eyes.
Why is only one of my eyes red?
A single red eye may be from a burst blood vessel, an early viral conjunctivitis, a foreign body or scratch, a contact lens problem, or more serious causes such as acute glaucoma, uveitis or keratitis. One red, painful eye with blurred vision needs same-day assessment.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Ophthalmology: Pink eye (conjunctivitis); Red eye causes
- American Academy of Family Physicians: Diagnosis and management of red eye in primary care
- NHS: Red eye
- College of Optometrists: Clinical management guidelines
- MedlinePlus: Eye redness