Which part of the poison ivy plant is responsible for its toxicity?

The toxicity of poison ivy is primarily attributed to the urushiol oil found in its sap. Urushiol is a potent allergen that can cause an allergic reaction upon contact with the skin. It can be present in various parts of the plant, but it is most concentrated in the sap, which is released when the plant is damaged, such as through cuts or crushing. This oil easily transfers to skin and clothing, leading to the characteristic rash and irritation associated with poison ivy exposure. While other parts of the plant may have some level of urushiol, the sap is the key factor responsible for the plant's toxic effects. Understanding this is crucial for identifying and avoiding contact with the plant, which can be helpful in preventing allergic reactions.