"Leaves of three, leave it be" serves as an apt caution for avoiding poison ivy (Toxicodendron species) and its dermatitis-inducing sap. Toxicodendron contact dermatitis (TCD) poses a notable burden to the American health care system by accounting for half a million reported cases of allergic contact dermatitis (ACD) annually. Identifying and avoiding physical contact with the western poison ivy (Toxicodendron rydbergii) plant prevails as the chief method of preventing TCD. This article discusses common features of T rydbergii as well as clinical manifestations and treatment options following exposure to this allergenic plant.