Urushiol is a natural oil found in the sap of plants like poison ivy, poison oak, and poison sumac. It is responsible for causing allergic reactions in many people who come into contact with these plants. The oil can trigger skin rashes, itching, and blisters, which can be uncomfortable and may require treatment. When exposed to urushiol, the body's immune system can react strongly, leading to a condition known as contact dermatitis. This reaction can occur within hours or days after exposure. To prevent reactions, it is important to recognize and avoid these plants, as well as to wash any skin or clothing that may have come into contact with them.