Poison Ivy, a plant native to North America. It grows along fences, in dry fields, and in open woodlands.

Common poison ivy is found throughout the United States. It is a climbing or trailing vine or upright shrub. It has alternate, compound leaves. Each leaf is composed of three dark-green leaflets 3 to 10 inches (8 to 25 cm) long. The leaflets are toothed or lobed and have pointed tips; they are usually glossy. The common poison ivy has yellowish-green flowers and greenish-white berries.

Poison ivyPoison ivy is composed of three dark-green leaflets.

The plant contains urushiol, an oily substance that is an allergen to most humans. It causes severe inflammation of the skin. Urushiol is present in all parts of the plantespecially the sap, which is most abundant in spring and summer. The poison is spread by contact with the plant or contaminated objects. It is also spread by burning the plantheat vaporizes the oil, which is then carried in the smoke. Urushiol on clothing, shoes, garden tools, and other objects can remain active for a year or longer.

Symptoms usually appear 24 to 48 hours after contact, but may take 7 to 10 days to develop. The skin develops a red, blistering rash that itches intensely. After about 5 days, the blisters break and become crusty. The skin usually heals within two weeks. The rash is treated with cortisone lotion or cream. Calamine lotion relieves the itching and inflammation and dries up the blisters. In severe reactions, oral doses of antihistamine, benzocaine, and corticosteroid drugs may be prescribed.

Poison ivy plants are killed by spraying with ammonium sulfamate or the herbicide 2, 4-D.

Common poison ivy is Rhus radicans of the cashew, or sumac, family, Anacardiaceae.