There are many possible causes of a red eye or eyes. Some are cause for concern; some are medical emergencies. Others are of no consequence or concern at all. The degree of redness or appearance of blood usually does not correlate to how serious the situation is. It is generally more important whether you also have eye pain or impaired vision.
Bloodshot eyes appear red because the vessels in the surface of the white portion of the eye (sclera) become enlarged and irritated. This may result from extremely dry air, sun exposure, dust, foreign body, an allergic reaction, infection, trauma, or other conditions.
One common cause of a red eye is straining or coughing. This can lead to a bright red, uniformly dense bloody area on the sclera. 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 blotch in one eye that doesn't hurt, but just looks bad, don't worry. It generally clears up on its own within a week or two.
Eye infections or inflammation can occur in different locations. They cause redness as well as possible itching, discharge, pain, or vision problems:
Other potential causes include:
For fatigue or eyestrain, try to rest your eyes. No treatment is necessary.
If you have conjunctivitis:
If you have blepharitis:
Go to the hospital or call your local emergency number (such as 911) if:
Call your health care provider if:
Your doctor will perform a physical exam, including an eye exam, and ask questions about your medical history. Questions may include:
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.
To prevent conjunctivitis:
Bloodshot eyes; Red eyes; Scleral infection; Conjunctival infection
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.
Updated by: A.D.A.M. Editorial Team: David Zieve, MD, MHA, and David R. Eltz. Previously reviewed by Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine (8/31/2010).
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