We've all experienced red, bloodshot eyes from time to time, affecting one or both eyes. Red eye is caused by swollen or dilated blood vessels on the sclera, the white outer surface of the eye. Red eyes can be accompanied by eye pain, itching, eye discharge, swollen eyes or visual disturbances such as blurry vision.In other cases, a red eye may cause no irritation at all.ed eyes usually are caused by allergy, eye fatigue, over-wearing contact lenses or common eye infections such as pink eye (conjunctivitis). However, redness of the eye sometimes can signal a more serious eye condition or disease, such as uveitis or glaucoma.