Pink, itchy eyes? Pink eye – or conjunctivitis – is common and spreads easily. It sometimes needs medical treatment, depending on the cause. Know the symptoms, when to seek treatment, and how to help prevent it. Pink eye, also known as conjunctivitis, is one of the most common and treatable eye conditions in the world in both children and adults. It is an inflammation of the conjunctiva, the thin, clear tissue that lines the inside of the eyelid and the white part of the eyeball.