Leviticus 13:38

“If a man also, or a woman, etc.] One or the other, for the law concerning leprosy respecteth both: have in the skin of their flesh bright spots; and them only; not any rising or swelling, nor scab, nor scall, nor boil, nor burning, only bright spots, a sort of freckles or morphew: [even] white bright spots; these, Ben Gersom observes, are white spots, but not plagues; and which were in whiteness inferior to the four species of the plague of leprosy, the white spot, the white swelling, and the scab of each.”

“If a man . . . or a woman have in the skin of their flesh bright spots--This modification of the leprosy is distinguished by a dull white color, and it is entirely a cutaneous disorder, never injuring the constitution. It is described as not penetrating below the skin of the flesh and as not rendering necessary an exclusion from society. It is evident, then, that this common form of leprosy is not contagious; otherwise Moses would have prescribed as strict a quarantine in this as in the other cases. And hereby we see the great superiority of the Mosaic law (which so accurately distinguished the characteristics of the leprosy and preserved to society the services of those who were laboring…”

“13:38-39 If a skin rash showed pus or inflammation (13:42), it was probably an infection. If it only showed as a whitened area, it was probably vitiligo (leucoderma). With this harmless disorder, patches of skin lose their pigmentation.”

“Harmless leprosy. - This broke out upon the skin of the body in בּהרת plaits, "white rings." If these were dull or a pale white, it was the harmless bohak, ἀλφός (lxx), which did not defile, and which even the Arabs, who still call it bahak, consider harmless. It is an eruption upon the skin, appearing in somewhat elevated spots or rings of inequal sizes and a pale white colour, which do not change the hair; it causes no inconvenience, and lasts from two months to two years. Leviticus 13:40”