Red eye is a common problem that can affect one or both eyes. The redness associated with red eye comes from expanded blood vessels on the surface of your eye due to inflammation, usually from some form of irritation or infection.
Most often the inflammation that causes red eye occurs in the membrane covering the white of your eye and lining your eyelid. This membrane is called the conjunctiva (kun-JUNK-tih-vuh); inflammation of the conjunctiva is called conjunctivitis (kun-junk-tih-VY-tis).
Click Here for more information about Red Eye from the Mayo Clinic.