The eye and its appendages are richly innervated by sensory nerves, especially the eyelids, conjunctiva and cornea, which are located on the body surface. When stimulated by inflammation as well as other disease factors, sensory neurons are able to induce signals that produce itch and pain and are further transmitted to the central nervous system, resulting in itchy, painful eyes. Common factors include conjunctivitis, blepharitis, dry eye, contact blepharitis, and many other diseases, as well as bad habits or exposure to chemicals, medications, sand, smoke, and other irritating factors.