Poison ivy is a plant that can cause skin irritation upon contact. It contains an oil called urushiol, which triggers allergic reactions in many people. The plant typically grows as a vine or shrub and is commonly found in wooded areas, fields, and gardens across North America. The leaves of poison ivy are usually grouped in sets of three and can vary in color from green to red, depending on the season. If someone comes into contact with the plant, they may develop an itchy rash, blisters, and swelling. It's important to wash the skin and clothing promptly to reduce the risk of a reaction.