There is nothing against it. I do not like the feel of many none cotton fabrics. I also did notice that the quilts I mixed cottons and poly cotton (Hawaiian prints) the poly cotton did not wear well and looks and feels less then the cottons in the quilt. My son loves that quilt though so it didn't matter and I got to use the cute prints. Also some of my children love the feel of the polyester those mumus are made with. I wished I felt comfortable enough to sew with that slippery stuff because I know it would mean a lot to them. They grew up in the islands and all the mamas and aunties wore those mumus.