Poison ivy is a type of woody vine known as Rhus radicans and Rhus toxicodendron. The vine produces a toxic resin known as urushiol that can cause intense itching and rashes in humans. It occurs in all of the United States except for Alaska, California, and Hawaii, and it is most often identified by its bright green color and three-leaf structure. While Poison ivy is a vine, it may also grow in a shrub like manner. Dogs and cats are rarely affected by Poison ivy. In many cases though, pet owners may contact Poison ivy when their pets bring the toxic resin home on their fur.