How could leprosy affect clothing?

Critics point out that leprosy cannot affect clothing –only skin. From this, they infer that the Bible is clearly a pre-scientific and pre-medical book, which is antiquated in its understanding of disease and medicine.

The key to understanding this objection is in the translation of the word “leprosy.” The Hebrew term for leprosy (tsara ‘ath) does not refer to the modern disease of leprosy (i.e. Hansen’s disease). Instead, this Hebrew word refers to skin disease in a more general sense. In fact, it is often associated with mildew or rot on a house (Lev. 14:34). When this term is used of skin, as in Leviticus 13:6, it can sometimes clear up in seven days, which is never true of Hansen’s disease. Therefore, this reference to tsara ‘ath on clothing probably refers to a general flaking or distorting of the garment, as it does in affecting people’s skin.