Fabric can catch on fire going through a laser printer, I've read. I have a Xerox Phaser laser printer, and it has a big warning not to put fabric through!
I did notice, however, printing numbers on Avery Labels will effectively number rows, etc., and when ironed, the print does not run, smudge, or transfer. Nice change from using pins with post-it notes or pieces of paper, to number the rows. Very handy!