it must be examined by a priest. If the infection seems more than skin deep, and the hair in it has thinned out and lost its color, he will say, "This is leprosy--you are unclean."
On the other hand, if he discovers that the itchy spot is only skin deep, but that the hair still isn't healthy, he will order you to stay away from everyone else for seven days.
These are the things you must do if you discover that you are unclean because of an itch or a sore, or that your clothing or house is unclean because of mildew.