Poison sumac is a woody shrub or small tree found primarily in wet, swampy areas of the eastern United States. It has compound leaves that typically consist of seven to thirteen leaflets, which are smooth and glossy. The plant produces clusters of small, greenish-white berries that can be toxic. Contact with any part of the poison sumac plant can cause skin irritation and allergic reactions in sensitive individuals. The rash is caused by an oil called urushiol, which is also found in poison ivy and poison oak. It is important to avoid touching the plant and to wash any exposed skin promptly.