I found this idea for Home made dryer balls, and tbh the commercial ones I used to use sounded like bricks being tumble dried so I quite fancy these. I've got loads of yarn hanging around, but being a cheapskate most of its acrylic.
You basically ball up some yarn, knot it into tights, wash repeatedly on 60 degrees and you should end up with felted balls that can be used for dryer balls and you can apparently put essential oils on.
www.tescoliving.com/articles/how-make-wool-dryer-balls
Mind you, I haven't got a pair of tights - it's strictly socks here.