Toxicodendron radicans, commonly known as poison ivy (older synonyms are Rhus toxicodendron and Rhus radicans), is a poisonous North American and Asian flowering plant that is well known for causing an itching, irritation and sometimes painful rash in most people who touch it, caused by urushiol, a clear liquid compound in the sap of the plant. It is variable in its appearance and habit, and despite its common name it is not a true ivy (Hedera). T. radicans is commonly eaten by many animals and the seeds are consumed by birds, but is most often thought of as a weed.