Conjunctivitis is an irritation or infection. It affects the membrane that covers the white of your eye and the inside of your eyelid (conjunctiva). It can happen to one or both eyes. The membrane swells and the blood vessels enlarge (dilate). This makes your eye red. That's why conjunctivitis is sometimes called red eye or pink eye.
If you have one or more of these symptoms, see an eye doctor:
Redness in and around your eye
Eyes that are puffy and sore
Itching, burning, or stinging eyes
Watery eyes or discharge from your eye
Eyelids that are crusty or stuck together when you wake up in the morning
Pink color in the whites of one or both eyes
Getting treatment quickly can help prevent damage to your eyes.
Conjunctivitis is usually a minor eye infection. But it can sometimes become a more serious problem. Some more serious eye diseases have symptoms that look like conjunctivitis. So it's important for an eye doctor to diagnose you. Your eye doctor will ask about your symptoms and any medicines you take. He or she will ask about any illnesses or medical conditions you may have. The doctor will also check your eyes with a hand-held light and a special microscope called a slit lamp.