If you...

Have catsHave a backyardLet the cats run around in the backyardAllow part of the backyard to be woodedDon't carefully tend the wooded part of the backyard (thus defeating the point of "wooded" for such inimical plant forms as poison ivyAllow the cats to run around in the wooded part of your backyardAllow the cats to rub all over you immediately after having run through the wooded parts of your backyard that have not been carefully tended for poison ivy and other inimical forms of plant life...