Conjunctivitis

Lore & Background

Conjunctivitis is identified by inflammation of the conjunctiva, manifested by irritation and redness. Examination using a slit lamp may improve diagnostic accuracy. The most common infectious causes in adults are viral, whereas in children bacterial causes predominate. Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Allergic conjunctivitis results from the release of histamine and other active substances by mast cells, causing redness, swelling, itching, and increased tear production.

Reader's Guide

Conjunctivitis is a common condition that affects millions annually, with viral causes accounting for approximately 80% of adult cases and bacterial causes responsible for about 70% of childhood cases. While most cases resolve without specific treatment, antibiotics can shorten bacterial infections, and antihistamines or mast cell inhibitor drops are used for allergic cases. Prevention partly relies on handwashing. The condition typically resolves in one to two weeks, but further diagnosis and treatment may be required if visual loss, significant pain, sensitivity to light, or signs of herpes occur, or if symptoms do not improve after a week. Neonatal conjunctivitis may also require specific treatment.

Did You Know?

• Between three and six million people get acute conjunctivitis each year in the United States.
• Approximately 80% of conjunctivitis cases in adults are due to viruses, with 65% to 90% of those caused by adenoviruses.
• Allergic conjunctivitis affects 15% to 40% of the population.
• Bacterial conjunctivitis in children is responsible for about 70% of cases, commonly caused by Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae.