Eye : Sight :: Skin : ? Choose the word that completes the analogy.

The relation is a sense organ : the one sense it carries to the brain. The eye gives sight; the skin gives touch. 'Sweat' is what the skin gives off and 'Hair' what grows out of it, so both are products rather than senses. 'Protection' is the nearest trap, being a genuine duty of the skin, but shielding the body is a job it performs and not a sense it supplies.