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Understanding Red Eye: Causes

Front view of eye showing red eye.Do your eyes sometimes get red and irritated? This could be a sign of irritation or infection. The inside of your eyelid and the white of your eye are covered with a membrane called the conjunctiva. When your eye is irritated or infected, the blood vessels in this membrane swell. This condition is called conjunctivitis. It is also known as red eye or pink eye.


Allergies and environmental irritants are common causes of inflamed eyes. Other causes can include:

  • Injuries

  • Objects in the eye

  • Some eye drops

  • Makeup

  • Contact lenses

  • Diseases within the eye


Viruses and bacteria can cause eye infections. An infection may begin in your eye. It can also start somewhere else in your body, such as your nose or throat. Sexually transmitted diseases can also cause eye infections.

Online Medical Reviewer: Bogus, William J., OD, FAAO
Online Medical Reviewer: Haupert, Christopher L., MD
Date Last Reviewed: 11/1/2017
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