This is all I know -- sometimes when I washed cat beds I would have to run an empty cycle to get all the cat hair out of the machine so we wouldn't have cat hair towels or something like that. I don't know about the dryer. I don't remember having a problem with hair inside the dryer. I would still have a lot of hair to take out of the dryer vent. I don't think I ever put anything hairy in the dryer without washing it first. Interesting. I have put pillows in the dryer to get dust out or for some reason. Didn't seem like it did much.