Conjunctivitis is an inflammation or infection of the membrane lining the eyelids (conjunctiva).

The conjunctiva is exposed to bacteria and other irritants. Tears help protect the conjunctiva by washing away bacteria. Tears also contain enzymes and antibodies that kill bacteria.

There are many causes of conjunctivitis. Viruses are the most common cause. Other causes include bacteria, Chlamydia, fungi, and rarely, parasites.

"Pink eye" refers to a viral infection of the conjunctiva. These infections are especially contagious among children.

Bacteria are an uncommon cause of 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. Use of contact lenses, particularly extended-wear lenses, can cause conjunctivitis.

See also:

• Allergic conjunctivitis
• Keratoconjunctivitis sicca
• Neonatal conjunctivitis
• Trachoma
• Vernal conjunctivitis

• Blurred vision
• Crusts that form on the eyelid overnight
• Eye pain
• Gritty feeling in the eyes
• Increased tearing
• Itching of the eye
• Redness in the eyes
• Sensitivity to light

• Examination of the eyes
• Swab of conjunctiva for analysis

Treatment of conjunctivitis depends on the cause.

Allergic conjunctivitis may respond to treatment for the underlying allergies, or it may disappear on its own when the allergen that caused it is removed. Cool compresses may be soothing for allergic conjunctivitis.

Antibiotic medication, usually eye drops, is effective for bacterial conjunctivitis. Viral conjunctivitis will disappear on its own. Many doctors give a mild antibiotic eyedrop for pink eye to prevent bacterial conjunctivitis.

You can soothe the discomfort of viral or bacterial conjunctivitis by applying warm compresses (a clean cloth soaked in warm water) to your closed eyes.

The outcome is usually good with treatment.

Reinfection within a household or school may occur if you don't follow preventive measures.

Call for an appointment with your health care provider if your symptoms last longer than 3 or 4 days.

Good hygiene can help prevent the spread of conjunctivitis:

• Change pillowcases frequently.
• Do not share eye cosmetics.
• Do not share towels or handkerchiefs.
• Handle and clean contact lenses properly.
• Keep hands away from the eye.
• Replace eye cosmetics regularly.
• Wash your hands often.