Conjunctivitis

Conjunctivitis, also known as pink eye or Madras eye,^[4][5] is inflammation of the conjunctiva, the thin, clear layer that covers the white surface of the eye and the inner eyelid.^[6] It makes the eye appear pink or reddish.^[1] Pain, burning, scratchiness, or itchiness may occur.^[1] The affected eye may have increased tears or be "stuck shut" in the morning.^[1] Swelling of the sclera may also occur.^[1] Itching is more common in cases due to allergies.^[3] Conjunctivitis can affect one or both eyes.^[1]

The most common infectious causes in adults are viral, whereas in children, bacterial causes predominate.^[7][3] The viral infection may occur along with other symptoms of a common cold.^[1] Both viral and bacterial cases are easily spread between people.^[1] Allergies to pollen or animal hair are also a common cause.^[3] Diagnosis is often based on signs and symptoms.^[1] Occasionally, a sample of the discharge is sent for culture.^[1]

Prevention is partly by handwashing.^[1] Treatment depends on the underlying cause.^[1] In the majority of viral cases, there is no specific treatment.^[3] Most cases due to a bacterial infection also resolve without treatment; however, antibiotics can shorten the illness.^[1][3] People who wear contact lenses and those whose infection is caused by gonorrhea or chlamydia should be treated.^[3] Allergic cases can be treated with antihistamines or mast cell inhibitor drops.^[3]

About 3 to 6 million people get acute conjunctivitis each year in the United States.^[1][3] Typically, people get better in one or two weeks.^[1][3] If visual loss, significant pain, sensitivity to light or signs of herpes occur, or if symptoms do not improve after a week, further diagnosis and treatment may be required.^[3] Conjunctivitis in a newborn, known as neonatal conjunctivitis, may also require specific treatment.^[1]