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 mistakenly identify it as a harmful substance, leading to an allergic response. The reaction typically occurs within 12 to 72 hours after contact and can last for several weeks. Proper identification and avoidance of these plants are essential to prevent exposure.