Pre-wash, gently. When I was working the sewing factory floor, I often hung new, cut fabric over my shoulder or around my neck when hurrying from task to task. Sometimes this caused skin irritation or even rash. Did not happen to my hands--tougher skin, maybe. So, pre-wash fabric because of dye/chemical residue AND pre-wash new clothing for the same reason PLUS--you cannot imagine how many hands an item goes through in production.