An eyelid is a thin piece of skin that covers and protects the eye. It is one of the thinnest areas of skin on a persons body. A muscle pulls back the eyelid to "open" the eye. People do this willingly or without thinking. The human eyelid has a row of eyelashes that help protect the eye from dust and other small objects. Eyelashes also keep sweat out of the eye. Eyelids regularly spread tears and other secretions on the surface of the eye to keep it moist. The cornea is one part of the eye that must be kept moist. Eyelids keep the eyes from drying out when asleep. Also, the blink reflex protects the eye from things touching it.