I've only made 2 rag quilts and it didn't occur to me they could cause problems. I must have gotten lucky because they both got washed in my front loader and dried in my dryer no problem. The flannel that I used was pretty tightly woven, so it probably didn't shed nearly as much as a homespun would. Also, I used rag snips and snipped the fabric after it was sewn rather than die cutting with a rag die and then sewing. Don't know if that would make a difference or not.