I would definitely wash it. You don't know whose cat it is unless you've since adopted it, and where it's been. I'm just not fond of any animal getting on my furniture or other stuff. I don't allow my dogs on my furniture and since they still have not found out how to do a running leap, I'm certainly not going to encourage it. I've always got a lint roller and shake as much hair off as possible before I throw it into the washer. I also give it another good shake before tossing into the dryer. Don't need anyone having any kind of allergic reaction.