The short answerMost red eyes are minor, such as a painless patch of blood under the surface of the eye, conjunctivitis, or dryness and irritation. A red eye is serious and needs to be seen the same day if it comes with real pain, reduced vision, strong light sensitivity, or halos around lights, if you wear contact lenses, if it follows an injury or a chemical splash, or if you have had recent eye surgery.
Common, usually harmless causes
Subconjunctival haemorrhage
A bright red patch on the white of the eye that appears suddenly, often after coughing, sneezing, lifting something heavy or rubbing the eye, and sometimes for no clear reason. It is painless, does not affect vision and clears on its own in about 1 to 2 weeks. If it keeps happening, or you take blood thinners or have high blood pressure, tell your doctor.
Conjunctivitis
- Viral: redness, watering and a gritty feeling, often starting in one eye and spreading to the other. It is contagious, so wash your hands and do not share towels.
- Bacterial: sticky yellow or green discharge and lids stuck together on waking.
- Allergic: strong itching in both eyes with watering, often with hay fever or at certain times of year.
Dryness and irritation
Mild redness with burning, worse with screens, air conditioning, smoke, dust and poor sleep. More about dry eye.
Probably minor, or see a doctor today?
| Symptom | What to do |
|---|---|
| A painless red patch with normal vision | Probably minor, keep an eye on it |
| Itching and watering in both eyes | Probably minor, routine check if it persists |
| Grittiness with a little discharge | Probably minor, get checked if no better in a few days |
| Real eye pain, not just burning | See a doctor today |
| Blurred or reduced vision that blinking does not clear | See a doctor today |
| Strong sensitivity to light | See a doctor today |
| Coloured halos around lights with pain, headache or vomiting | Emergency, go now |
| A painful red eye in a contact lens wearer | See a doctor today |
| An injury, something in the eye, or a chemical splash | Emergency, go now; for chemicals rinse first |
| Redness after recent eye surgery | Call your surgeon or get seen today |
Contact lens wearers: take care
A painful red eye in someone who wears contact lenses can be the start of a corneal infection or ulcer, which can leave permanent damage to vision if treatment is delayed. Take the lens out straight away, do not put it back in, keep the lens and its case, and get seen the same day.
Chemical in the eye: what to do right away
Rinse the eye immediately with plenty of clean running water for at least 15 minutes, holding the lids wide open. Do not wait until you reach hospital to start rinsing. Then go straight to the emergency department, taking the product container with you if you can. Alkalis such as lime and strong cleaning products are especially dangerous.
Avoid steroid drops without a doctor
Steroid eye drops can calm redness for a while, but using them without an exam can make some infections worse, especially herpes virus and fungal infections of the cornea. With long use they can also raise eye pressure or cause cataract. Do not use drops prescribed for a previous problem or for someone else.
Frequently asked questions
My eye is red but doesn't hurt. What should I do?
If it is a red patch with no pain and normal vision, it is most likely a small bleed under the surface that clears in 1 to 2 weeks. If it keeps coming back, or you take blood thinners or have high blood pressure, tell your doctor.
When is a red eye an emergency?
When it comes with real pain, reduced vision, strong light sensitivity, or halos around lights with headache, after an injury or chemical splash, in a contact lens wearer, or after recent eye surgery.
Is conjunctivitis contagious?
Viral and bacterial conjunctivitis are contagious. Wash your hands often, avoid touching your eyes, and do not share towels or make-up. Allergic conjunctivitis is not contagious.
Can I use steroid eye drops for a red eye?
Not without an exam. They may hide symptoms for a while but can make some corneal infections worse, and long use can raise eye pressure.