Poison ivy (Toxicodendron radicans) is a vine. It is well-known for causing a rash. The rash is urushiol-induced contact dermatitis. Urushiol is the chemical in the ivy that hurts the skin. The plant grows the urushiol so animals will not eat it. The rash itches and it can cause pain.
The vine's leaves come in threes, with a shiny appearance caused by the oil on the leaves. It is a common weed in the eastern North America and parts of China.