Conjunctivitis is an irritation or infection. It affects the conjunctiva. This is the membrane that covers the white of your eye and the inside of your eyelid. 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 care provider:

• 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 white of one or both eyes
• Sensitivity to bright light

Getting treatment quickly can help prevent damage to your eyes.

Conjunctivitis is often a minor eye infection. But it can sometimes become a more serious problem. Some more serious eye diseases have symptoms that look like conjunctivitis. It's important for an eye care provider to diagnose you. Your eye care provider will ask about your symptoms and any medicines you take. They will ask about any illnesses or health conditions you may have. Your eye care provider will also check your eyes with a handheld light and a special microscope called a slit lamp.