Fabric is required to be treated with formaldehyde for shipping purposes. It kills any bugs that may find their way into the bolt, preventing foreign insects from being introduced into the country. After a day of cutting fabric at the shop, my hands have a slimy chemical coating on them. You bet your buttons I prewash all my fabric! (Except for precuts...but they do get washed after the quilt is made). Actually, I don't buy precuts very often for this reason.