Leprosy is a contagious skin disease found more frequently in hot countries. It is communicated by contact. First the hands, face and exposed parts are attacked, and then the whole of the flesh corrupts and dies by slow stages. Lepers had to remain outside the camp of Israel. Some leprosy was curable and a cured leper could return into the camp after inspection by the priest, and a thank offering had been made on the altar. Clothing, household goods and building materials could also be 'leprous' and had to be destroyed by fire if they could not be washed clean. Leprosy in materials was probably some form of mould or rot. The word 'leprosy' may have described various skin conditions, most of them being different from the condition called leprosy today.

The most notable leper in the Old Testament was Naaman the Syrian, who was cured by the prophet Elisha (in 2 Kings 5), and in the Gospels, lepers came to Jesus to be cured (see Luke 5:12-16).