Conjunctivitis is an infection or irritation of the conjunctiva, the thin, clear tissue covering the white part of your eye and the inside of your eyelids. When you have conjunctivitis, your eyes turn pink or red, feel itchy or scratchy, and might produce a sticky discharge that can make your eyelids crusty, especially after sleeping.

The condition is often called pink eye because of how it makes the white part of your eye look. You can get conjunctivitis from a virus (like the common cold), bacteria, allergies to pollen or pet dander, or irritants like chlorine in swimming pools or smoke. The viral and bacterial types spread easily from person to person through touching your eyes with unwashed hands or sharing things like towels or pillows.

Schools often send kids with conjunctivitis home because it spreads so quickly: one student rubs their infected eye, touches a doorknob, and then other students touch that same doorknob and later rub their own eyes. Most cases clear up on their own within a week, though bacterial conjunctivitis might need antibiotic eye drops. Washing your hands often and trying not to touch your eyes can help prevent it from spreading.