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Eye Redness


Christopher J. Brady

, MD, Wilmer Eye Institute, Retina Division, Johns Hopkins University School of Medicine

Last full review/revision Jun 2021| Content last modified Jun 2021
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Topic Resources

Eye redness refers to a red appearance of the normally white part of the eye. The eye looks red or bloodshot because blood vessels on the surface of the eye widen (dilate), bringing extra blood into the eye. Pink eye typically refers to eye redness caused by a specific viral infection.

Blood vessels can dilate as a result of

  • Infection

  • Allergy

  • Inflammation caused by something other than an infection

  • Elevated pressure inside the eye, typically caused by sudden, closed-angle glaucoma, in which fluid pressure increases in the front chamber of the eye

Several parts of the eye may be affected, most commonly the conjunctiva (the thin membrane that lines the eyelid and covers the front of the eye), but also the iris (the colored part of the eye), the sclera (the tough white fiber layer covering the eye), and the episclera (the connective tissue layer between the sclera and the conjunctiva).

An Inside Look at the Eye

An Inside Look at the Eye

Rarely is eye redness the only eye symptom. People may have tearing, itching, the feeling that a foreign object is in the eye (foreign body sensation), sensitivity to light, pain, or even changes in vision. Sometimes people have symptoms that affect other areas of the body, such as a runny nose or cough, or nausea and vomiting.


Many disorders can cause eye redness. Some are emergencies, but others are mild and go away without treatment. The degree of redness does not indicate the seriousness of the disorder. The presence of eye pain or vision problems is more likely to suggest a serious cause.

The most common causes of eye redness are

  • Inflammation of the conjunctiva caused by an infection (infectious conjunctivitis, or pink eye)

  • Inflammation of the conjunctiva caused by an allergic reaction (allergic conjunctivitis)

Scratches of the cornea (the clear layer in front of the iris and pupil) and foreign objects in the eye are also common causes of eye redness. In these cases, however, the person is more likely to consider the problem to be an eye injury, eye pain, or both. Corneal scratches may be caused by contact lenses or by foreign objects or tiny particles trapped under the eyelid. Occasionally, very dry air can cause some eye redness and irritation.

Serious causes of eye redness are much less common. They include corneal ulcers, herpes simplex keratitis (herpes infection in the cornea), herpes zoster ophthalmicus (shingles in or around the eye), acute closed-angle glaucoma, anterior uveitis, and scleritis (a deep, painful inflammation of the sclera).


Some Causes and Features of Eye Redness


Common Features*

Diagnostic Approach†

Conjunctival disorders and episcleritis‡

Allergic or seasonal conjunctivitis (inflammation of the conjunctiva—the membrane that lines the eyelid and covers the front of the eye)

Affecting both eyes

An itching or scratching sensation and tearing

In people with known allergies or other features of allergies (such as a runny nose that recurs during certain seasons)

Sometimes in people who use eye drops (particularly neomycin)

A doctor's examination alone

Chemical (irritant) conjunctivitis

An itching or scratching sensation and tearing

Exposure to potential irritants (such as dust, smoke, ammonia, or chlorine)

A doctor's examination alone

Episcleritis (inflammation of the tissue between the sclera—the white of the eye—and the overlying conjunctiva)

Affecting only one eye

A spot of redness on the white of the eye

Mild irritation of the eye

A doctor's examination alone

An itching or scratching sensation, tearing, and sensitivity to light

Sometimes a discharge from the eye and eyelid swelling

Sometimes swollen lymph nodes in front of the ears

A doctor's examination alone

Subconjunctival hemorrhage (bleeding under the conjunctiva)

Affecting only one eye

A red patch or large area of redness (that looks like blood or ketchup)

No tearing, irritation, itching, change in vision, pain, or discharge from the eye

Sometimes in people who have had an eye injury, sneezed violently, or tried to exhale without letting air escape, as may occur during a bowel movement or while lifting a heavy weight (called the Valsalva maneuver)

Often in people known to use drugs that help prevent blood from clotting (such as aspirin or warfarin)

A doctor's examination alone

Corneal disorders§

Contact lens keratitis (inflammation of the cornea—the clear layer in front of the iris and pupil)

Eye ache, redness, tearing, and sensitivity to light

In people who have worn their contact lenses for too long

A doctor's examination alone

Corneal scratch (abrasion) or foreign object (body)

Symptoms that begin after an eye injury (which may not have been noticed in infants and young children)

Pain when blinking and a foreign body sensation

A doctor's examination alone

Sometimes a grayish patch on the cornea that later becomes an open, painful sore

Sometimes in people who have had an eye injury or who slept with their contact lenses in

A doctor's examination

Culture of a sample taken from the ulcer (done by an ophthalmologist)

Epidemic keratoconjunctivitis (Pink Eye—inflammation of the conjunctiva, the membrane that lines the eyelids and covers the front of the eye, and the cornea caused by an adenovirus)

Watery discharge

Eyelid swelling, enlarged lymph nodes and bulging of conjunctiva

Sometimes temporary loss of vision

A doctor's examination alone

Herpes simplex keratitis (infection of the cornea caused by the herpes simplex virus)

Affecting only one eye

Early: Blisters on the eyelid and/or crusting

Late or recurring: Eye redness and tearing, eye pain, impaired vision, and sensitivity to light

A doctor's examination

Sometimes, testing for the virus in scrapings obtained from the surface of the cornea or from blisters around the eye

Herpes zoster ophthalmicus (shingles that affects the face and eye, caused by the varicella-zoster virus)

Affecting only one eye

Early: A rash with fluid-filled blisters and/or crusting on one side of the face, around the eye, on the forehead, and/or on the tip of the nose, and sometimes pain

Eye redness, tearing, and eyelid swelling

Late: Eye redness, usually sensitivity to light, and usually severe pain

A doctor's examination

Sometimes, testing for the virus in scrapings obtained from blisters around the eye

Other disorders

Severe eye ache and redness

Headache, nausea, vomiting, and pain with exposure to light

Disturbances in vision such as seeing halos around lights and/or decreased vision

Measurement of pressure inside the eye (tonometry) and examination of the eye's drainage channels with a special lens (gonioscopy), done by an ophthalmologist

Anterior uveitis (inflammation of the anterior chamber—the fluid-filled space between the iris and cornea)

Eye ache and sensitivity to light

Eye redness (particularly around the cornea)

Blurring or loss of vision

Often in people who have an autoimmune disorder or who recently had an eye injury

A doctor's examination alone

Scleritis (inflammation of the white of the eye, called the sclera)

Pain, often described as boring, and severe enough to wake someone from a sound sleep

Sensitivity to light


Red or violet patches on the white of the eye

Often in people who have an autoimmune disorder

A doctor's examination

Sometimes, ultrasound, or CT of the orbits

Rarely, biopsy

* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

† Although a doctor's examination is always done, it is mentioned in this column only if the diagnosis can sometimes be made only by the doctor's examination alone, without any testing. If an ophthalmologist's examination is specifically required, that is mentioned separately.

‡ Conjunctival disorders usually cause itching or a scratchy sensation, tearing, widespread eye redness, and often sensitivity to light. They usually do not cause pain or changes in vision.

§ Corneal disorders usually cause pain (particularly when the eyes are exposed to light), tearing, and sometimes impaired vision.


Not every case of eye redness requires evaluation by a doctor. The following information can help people decide when to see a doctor and to know what to expect during an evaluation. In most cases, people with eye redness can be evaluated by a general health care practitioner rather than an ophthalmologist (a medical doctor who specializes in the evaluation and treatment—surgical and nonsurgical—of eye disorders).

Warning signs

In people with eye redness, certain symptoms and characteristics are cause for concern. They include

  • Sudden, severe pain and vomiting

  • Rash on the face, particularly around the eyes or on the tip of the nose

  • Decreased sharpness of vision (visual acuity)

  • An open sore on the cornea

When to see a doctor

Deep eye pain should be distinguished from irritation. People who have warning signs, particularly deep pain or a change in vision, should see a doctor right away. If no warning signs are present, it is safe to wait a couple of days or so, but people may want to see a doctor sooner so that they can start treatment quickly.

What the doctor does

Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What they find during the history and physical examination often suggests a cause of eye redness and the tests that may need to be done (see table Some Causes and Features of Eye Redness).

Doctors ask

  • How long redness has been present

  • Whether redness has occurred before

  • Whether there is pain or itching

  • Whether there is discharge or the eyes are tearing

  • Whether there is a change in vision

  • Whether there has been an eye injury

  • Whether the person wears contact lenses and whether they have been overused

  • Whether the person has been exposed to substances (such as dust or eye drops) that could irritate the eyes

  • Whether there are other symptoms (such as headache, halos around lights, runny nose, cough, or sore throat)

  • Whether the person has allergies

Pain together with nausea or vomiting or halos around lights is a potentially serious combination of symptoms. These symptoms often occur in acute closed-angle glaucoma. Pain and sensitivity to light may indicate a disorder of the cornea, such as a scratch or a foreign object. An absence of pain and sensitivity to light may indicate a disorder of the conjunctiva.

During the physical examination, doctors examine the head and neck for signs of disorders that may cause eye redness, such as runny nose and cough that may indicate an upper respiratory infection or allergy or a rash that may indicate shingles (herpes zoster infection).

The eye examination is the most important part of the physical examination. Doctors check the person's eye and the area around the eye for injuries or swelling. They check the person's vision (with glasses or contacts if the person wears them), pupil size and response to a light, and eye movement.

Doctors use a slit lamp (an instrument that enables a doctor to examine the eye under high magnification) to examine the eye. Doctors put a drop of anesthetic and then a drop of fluorescein stain in the eye to diagnose corneal disorders. While the eye is anesthetized, pressure inside the eye (intraocular pressure) is often measured (called tonometry).

If pain develops in the affected eye (particularly if it is shut at this time) when a light is shined in the unaffected eye, the problem may be anterior uveitis or a corneal disorder. The use of an anesthetic makes the examination easier, and the person's response to the anesthetic may be a clue to the diagnosis. Anesthetic eye drops do not relieve pain that is caused by glaucoma, uveitis, or scleritis.


Testing is usually unnecessary.

If doctors suspect a viral infection (herpes simplex virus or varicella-zoster virus), they may take samples of discharge or blister fluid to send to the laboratory. The sample is placed in a culture medium (a substance that allows bacteria or viruses to grow). Samples for culture may also be taken when the person has a corneal ulcer so doctors can give antibiotics that are most likely to be effective. Gonioscopy (use of a special lens to examine the drainage channels in the eye) is done in people with glaucoma. Sometimes people with uveitis are tested for autoimmune disorders, especially if there is no obvious cause (such as an injury) for the uveitis.

People with scleritis are usually referred to an ophthalmologist who often does additional tests.


The cause is treated. Eye redness itself does not require treatment. It usually clears up on its own as the cause resolves (for example, a few days for infectious conjunctivitis or a couple of weeks for subconjunctival hemorrhage). Cool washcloths or artificial tears can be applied if any itching is particularly bothersome. Eye drops that aim to eliminate redness (available over-the-counter) are not recommended.

Key Points

  • Usually, eye redness is caused by conjunctivitis.

  • Pain, a rash around the eye or nose, and changes in vision suggest a potentially serious cause.

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Test your knowledge

Herpes Zoster Ophthalmicus
Herpes zoster ophthalmicus is an infection of the eye caused by the varicella-zoster virus. This virus also causes chicken pox and shingles. Which of the following describes the mechanism by which herpes zoster ophthalmicus causes infection?
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