We had two lovely sheepskins, when we got a kitten we sprayed one with flea spray, and it made the wool go all sticky and rough, so we didn't spray the other.
I found this online, and thought was try it out. It was simple to use and put the rug in on a 'wool' wash, then lay it out in the garden to dry, turning it alternately onto its front and back every few hours (to make sure both the leather and the wool dried properly) took a few days to be fully dry. I then brushed it with a pet brush, and it's now lovely and soft again, and looks good as new.
Ours was a dyed sheep skin, and this did not seem to remove any of the colour.