Leviticus 13:19-20

13:19 and in the place of the boil there is a white swelling or a reddish white bright spot, he must show himself to the priest. 13:20 The priest will then examine it, and if it appears to be deeper than the skin and its hair has turned white, then the priest is to pronounce the person unclean. It is a diseased infection that has broken out in the boil.