Eye redness is due to swollen or dilated blood vessels, which cause the surface of the eye to look red, or bloodshot.
Bloodshot eyes; Red eyes; Scleral infection; Conjunctival infection
There are many possible causes of a red eye or eyes. Some are cause for concern; some are medical emergencies. Others are nothing to worry about.
How red the eye appears is often less of a concern than whether you also have eye pain or difficulty seeing.
Bloodshot eyes appear red because the vessels in the surface of the white portion of the eye (sclera) become swollen. This may result from dry air, too much sun, dust, something in the eye, allergies, infection, or injury.
One common cause of a red eye is straining or coughing. This can lead to a bright red, dense bloody area on the white part of the eye. This is called a subconjunctival hemorrhage. Although this bloody area may appear alarming, it is a fairly common occurrence and of little significance. If you notice a bloody spot in one eye that doesn't hurt, but just looks bad, don't worry. It should clear up on its own within a week or two.
Eye infections or inflammation can occur, causing redness as well as possible itching, discharge, pain, or vision problems:
Blepharitis -- Swelling of the eyelash along the edge of the eyelid.
Conjunctivitis -- Swelling or infection of the tissue that lines the eyelids and coats the surface of the eye (the conjunctiva). This is often referred to as "pink eye."
Corneal ulcers -- Ulcers on the outer covering of the eye, usually because of a bacterial or viral infection.
Uveitis -- Swelling of the uvea, which includes the iris, ciliary body, and choroid. This is often related to an autoimmune disorder, infection, or exposure to toxins. Often, only the iris is inflamed, which is called iritis.
Other potential causes include:
Cold or allergies.
Acute glaucoma -- a sudden increase in eye pressure that is extremely painful and causes serious visual disturbances. This is a medical emergency. Most times, glaucoma is chronic and gradual.
Corneal scratches caused by sand, dust, or overuse of contacts.
For fatigue or eyestrain, try to rest your eyes. No treatment is necessary.
If you have eye pain or a vision problem, call your doctor or nurse.
Call your health care provider if
Go to the hospital or call your local emergency number (such as 911) if:
Your eye is red after a penetrating injury.
You have a headache along with blurred vision or confusion.
You take blood thinning medication, like warfarin.
You may have an object in your eye.
You are very sensitive to light.
You have a yellow or greenish discharge from one or both eyes.
What to expect at your health care provider's office
Your doctor will perform a physical exam, including an eye exam, and ask questions about your medical history. Questions may include:
Are both of your eyes affected? If only one eye, which one?
What part of the eye is affected -- the white part, or elsewhere?
Did the redness come on suddenly?
Have you ever had eye redness before?
Do you have eye pain? Does it get worse after movement of the eyes?
Do you have other symptoms like eye discharge, burning, or itching? Nausea or vomiting? A headache?
The eyes may need to be washed out with normal saline solution, and any foreign bodies will need to be removed. Eye drops may be prescribed.
Wright JL, Wightman JM. Red and painful eye. In: Marx JA, ed. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 32.
Rubenstein JB, Virasch V. Conjunctivitis: Infectious and noninfectious. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, Mo: Mosby Elsevier; 2008:chap 4.6.
Yanoff M, Cameron D. Diseases of the visual system. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 431.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.