What is an eye infection? An eye infection is a bacterial or viral infection of the eye or the tissue immediately surrounding the eye. Common eye infections include conjunctivitis, often called pink eye, which affects the membrane that lines the inside of your eyelids and covers the whites of the eyes, and blepharitis, which affects the eyelid margin. Although infections of the cornea, the clear “window” over the center of your eye, are not common, they can seriously affect your vision. The use of contact lenses contributes to eye infections if worn for extended periods or without proper cleaning. Eye infections often cause redness, irritation, tearing and itchiness. Discharge from the eye and crusting of the eyelid margin are also common symptoms that may cause your eyelids and lashes to feel stuck together when you awaken. You may also experience eye pain and swelling of the tissues around the eye. These symptoms can also appear in allergies, and you may need to see your health care provider to determine whether you have an allergy or an infection. Eye infections can affect one or both eyes, and they may occur at any age, though they are most common in children and young adults. Some eye infections are highly contagious, and you must take care not to infect other people, or even your other eye, if only one eye is infected. In some cases, allergies or irritation can cause symptoms similar to an eye infection. Additionally, eye allergies and eye irritation and can make it easier for you to get an eye infection. Eye infections caused by viruses are generally mild and usually resolve on their own with a week or two. An exception is eye infection caused by herpes simplex virus, which can be a serious eye infection. Bacterial eye infections often require antibiotic treatment. Because a serious eye infection can affect vision, it is important to see a physician if your symptoms are severe or last longer than about two days. If you have any changes in vision, you should contact your health care provider immediately. Seek immediate medical care (call 911) for an eye infection along with other serious symptoms, including visual changes, high fever (higher than 101 degrees Fahrenheit), severe headache, stiff neck, lethargy, and extreme sensitivity to light; if swelling around your eye is severe and restricts movement of your eye; or if eye symptoms occur along with constriction of the throat or difficulty breathing. Seek prompt medical care if you have an eye infection that does not improve within a few days or if you are being treated for an eye infection but mild symptoms recur or are persistent.