Poison ivy - oak - sumac rash

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Poison ivy on the knee

Poison ivy on the leg

Poison oak rash on the arm

Rash

Poison ivy, oak, and sumac are plants that commonly cause an allergic skin reaction. The result is typically an itching, red rash with bumps or blisters.

Poison ivy is one of the most frequent causes of skin rash among children and adults who spend time outdoors. The plant can be found throughout the United States, except in the Southwest, Alaska, and Hawaii. It has three shiny green leaves and a red stem. Poison ivy typically grows in the form of a vine, often along riverbanks.

Poison oak is primarily found on the West Coast. It grows in the form of a shrub and has three leaves similar to poison ivy.

Poison sumac grows abundantly along the Mississippi River. It grows as a woody shrub. Each stem contains 7-13 leaves arranged in pairs.

The rash is caused by skin contact with the oily sap (or resin) of these plants. Smoke from burning these plants can cause the same reaction. The oily resin usually enters the skin rapidly, and is seldom transferred from person to person. The rash is NOT caused by the fluid from the blisters. Thus, once the person has washed the oil off the skin, the rash is usually not contagious.

Keep in mind that the resin may last for long periods on contaminated clothing, pets, tools, shoes, and other surfaces. These contaminated items can cause future rashes long after the initial exposure.

Review Date: 05/15/2006
Reviewed By: Eric Perez, MD, Department of Emergency Medicine, St. Luke's-Roosevelt Hospital Center, New York, NY. Review provided by VeriMed Healthcare Network.