Poison oak is a plant that can cause skin irritation and allergic reactions in many people. It typically grows as a shrub or vine and is found in the western and southeastern regions of the United States. The leaves are usually grouped in clusters of three and can have a glossy appearance, turning red or orange in the fall. Contact with any part of the plant, including the leaves, stems, and roots, can lead to a rash characterized by itching, redness, and blisters. The rash is caused by an oil called urushiol, which is present in the plant. Avoiding contact and recognizing the plant are key to preventing reactions.