Exodus 9:8-11:

And the LORD said unto Moses and unto Aaron, Take to you handfuls of ashes of the furnace, and let Moses sprinkle it toward the heaven in the sight of Pharaoh.
And it shall become small dust in all the land of Egypt, and shall be a boil breaking forth with blains [inflammatory pustules] upon man, and upon beast, throughout all the land of Egypt.
And they took ashes of the furnace, and stood before Pharaoh; and Moses sprinkled it up toward heaven; and it became a boil breaking forth with blains upon man, and upon beast.
And the magicians could not stand before Moses because of the boils; for the boil was upon the magicians, and upon all the Egyptians.

Notes on Exodus 9:8-11:

Boils are a curse!  There is no reason for such a curse to be on a Christian.  You can command them to be gone because Christ has redeemed you from the curse of boils.

See also:

Sickness as Chastening and Judgment in the Old Testament
Condition: Boils