Conjunctivitis is inflammation or infection of the membrane lining the eyelids (conjunctiva).
Alternative Names
Inflammation - conjunctiva; Pink eye
Causes, incidence, and risk factors
The conjunctiva is exposed to bacteria and other irritants. Tears help protect the conjunctiva by diluting bacteria and washing it away. Tears also contain enzymes and antibodies which kill bacteria.
There are many causes of conjunctivitis. Viruses are the most common cause. Other causes include bacteria, Chlamydia, fungus, and rarely, parasitic agents.
"Pink eye" refers to a viral infection of the conjunctiva. These infections are especially contagious among children. Handwashing is key to preventing the spread of the virus, which is similar to the type that cause the common cold.
Bacteria are an uncommon cause of conjunctivitis. Many physicians give a mild antibiotic eyedrop for pink eye to prevent bacterial conjunctivitis. Conjunctivitis is also caused by allergies (allergic conjunctivitis), chemical exposure, and certain systemic (throughout the body) diseases.
Newborns can be infected by bacteria in the birth canal. This condition is called ophthalmia neonatorum, and it must be treated immediately to preserve eyesight.
Allergic conjunctivitis (3 images)(Doctor-Reviewed information)
Allergic conjunctivitis describes the eye's reaction to allergy-causing substances like pollen and dander. It usually includes redness, tearing, and itching. Reviewer: Manju Subramanian, MD, Assistant Professor in Ophthalmology, Vitreoretinal Disease and Surgery, Boston University Eye Associates, Boston, MA. Review provided by VeriMed Healthcare Network.Date: 09/01/2006
Vernal conjunctivitis (1 image)(Doctor-Reviewed information)
Vernal conjunctivitis is a seasonal inflammation of the outer lining of the eyes, which is thought to be due to an allergic reaction. Reviewer: Paul B. Griggs, MD, Department of Ophthalmology, Virginia Mason Medical Center, Seattle, WA. Review provided by VeriMed Healthcare Network.Date: 05/19/2006
Neonatal conjunctivitis(Doctor-Reviewed information)
Neonatal conjunctivitis is a red eye in a newborn caused by irritation, a blocked tear duct, or infection. Reviewer: Deirdre OReilly, MD, MPH, Neonatologist, Division of Newborn Medicine, Childrens Hospital Boston and Instructor in Pediatrics, Harvard Medical School, Boston, Massachusetts. Review Provided by VeriMed Healthcare Network.Date: 10/15/2007
Trachoma (1 image)(Doctor-Reviewed information)
Trachoma is an eye infection caused by bacteria. Reviewer: Manju Subramanian, MD, Assistant Professor in Ophthalmology, Vitreoretinal Disease and Surgery, Boston University Eye Associates, Boston, MA. Review provided by VeriMed Healthcare Network.Date: 09/22/2006
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