The skin protects man's flesh, but when the skin fails it becomes infected, and forms into sores and boils. And the boil of a leper would remain, for the leper would be left with a mark on his skin. And the Son made the scales of the leprosy clean. But man has refused to have his sins cleaned. "For thus says the LORD, 'Your wound is incurable and your injury is serious. There is no one to plead your cause; no healing for your sore, no recovery for you."
The skin covers man's flesh, but when the skin is broken it forms into sores and boils. And the Lord inflected Egypt with a plague of sores and boils. "Then the LORD said to Moses and Aaron, 'Take for yourselves handfuls of soot from a kiln, and let Moses throw it toward the sky in the sight of Pharaoh. It will become fine dust over all the land of Egypt, and will become boils breaking out with sores on man and beast through all the land of Egypt. So they took soot from a kiln, and stood before Pharaoh; and Moses threw it toward the sky, and it became boils breaking out with sores on man and beast. The magicians could not stand before Moses because of the boils, for the boils were on the magicians as well as on all the Egyptians." (Exodus 9:8-11) And Satan smote Job with boils among ashes. "Then Satan went out from the presence of the LORD and smote Job with sore boils from the sole of his foot to the crown of his head. And he took a potsherd to scrape himself while he was sitting among the ashes." (Job 2:7-8) And God promised that He would curse man with boils. "The LORD will strike you on the knees and legs with sore boils, from which you cannot be healed, from the sole of your foot to the crown of your head. The LORD will bring you and your king, whom you set over you, to a nation which neither you nor your fathers have known, and there you shall serve other gods, wood and stone. You shall become a horror, a proverb, and a taunt among all the people where the LORD drives you." (Deuteronomy 28:35-37)