Red eye

A red eye can be alarming, but is often just a sign of a minor eye condition, such as conjunctivitis or a burst blood vessel. If it's painful, there may be a more serious problem.

The following information aims to give you a better idea about what might be causing your red eye. But it shouldn't be used to self-diagnose your condition. Always see a doctor for a proper diagnosis and treatment.

When to get medical advice

See your GP for advice if you have a red eye that doesn't start to improve after a few days.

Contact your GP or NHS 111 immediately or go to your nearest accident and emergency (A&E) department if:

• you have a painful red eye
• you have other symptoms, including any changes in your vision, sensitivity to light, a severe headache and feeling sick
• you've recently injured your eye, particularly if something has pierced it

Common causes of a painless red eye

The most likely causes of a painless red eye are minor problems such as conjunctivitis or a burst blood vessel. These conditions don't tend to affect your vision and usually get better within a week or two.

Conjunctivitis

Conjunctivitis causes the blood vessels on the eye to swell, making one or both eyes look bloodshot and feel gritty.

Other symptoms can include itchiness and watering of the eyes, and a sticky coating on the eyelashes.

Conjunctivitis can be caused by an infection, an allergy (for example, to pollen), or an irritant like chlorine or dust.

Treatment will depend on what's causing the condition. Sometimes treatment isn't needed because it may get better on its own.

Read more about treating conjunctivitis.

Burst blood vessel in the eye

Straining, coughing or injuring your eye can sometimes cause a blood vessel to burst on the surface of the eye, resulting in a bright red blotch.

It can look alarming, particularly if you're taking medication like aspirin or warfarin as these reduce the blood's ability to clot, which can exaggerate the redness, but it's not usually serious and should clear up on its own within a few weeks.

Common causes of a painful red eye

If your red eye is painful or you have other symptoms, such as changes in your vision, it should be assessed by a doctor as soon as possible.

Uveitis

Uveitis is inflammation of the iris, the coloured part of the eye. It's also known as iritis.

As well as a red eye, your eye may be sensitive to light, your vision may be blurred, and you may have a headache.

Uveitis usually responds quickly to treatment with steroid medication to reduce the inflammation. It rarely leads to severe problems.

Read more about uveitis.

Glaucoma

Glaucoma is an eye condition where the optic nerve, which connects your eye to your brain, becomes damaged.

Your eye will probably be very red and painful, and you may feel sick and see halos around lights. Your vision may be blurred or cloudy.

If your GP thinks you may have glaucoma, they'll refer you to an eye specialist called an ophthalmologist immediately. This is because it could lead to a permanent loss of vision if not treated quickly.

Read more about glaucoma.

Corneal ulcer (ulcer on the cornea)

An ulcer on the cornea, the clear outer layer at the front of the eyeball, can make the eye red and sensitive to light. It can also feel like there's something in your eye.

People who wear contact lenses have an increased risk of getting bacterial corneal ulcers. Viral corneal ulcers are more likely to affect people who often get cold sores.

If your GP thinks you have a corneal ulcer, they'll refer you to an eye specialist for treatment.

A scratch to the cornea or particle in the eye

A red and painful eye can sometimes be caused by a particle, such as a piece of grit, getting in your eye.

If there's something in your eye, your GP or a hospital doctor at an A&E department will try to remove it. They'll first put anaesthetic eye drops into your eye to numb it and reduce further discomfort.

If the particle has scratched your eye, it may feel a bit uncomfortable when the anaesthetic wears off. You may be given antibiotic eye drops or ointment to use for a few days to reduce the risk of infection while it heals.

Read more about eye injuries.