TT #70 · Parshas Tazria · Aliyah 1 · Passuk 2
English: When a person has on the skin of the body a swelling, a rash, or a discoloration, and it develops into a scaly affection on the skin of the body, it shall be reported to Aaron the priest or to one of his sons, the priests.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:2
Torah Temimah cites Sifra (Toras Kohanim) for including skin locations that are not suited to growing hair.
Sifra — Vayikra 13, Midrash Sefer
English: “On the skin of his flesh” — to include even a place not fit to grow hair.
Textual inclusion
A location is not excluded from the skin-affliction laws merely because it naturally does not grow hair.