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Poison Ivy, Oak, and Sumac

Poison Ivy, Oak, and Sumac Overview

More than half the people in the United States are sensitive to poison ivy, poison oak, and poison sumac. If an individual is sensitive, he or she can develop an itchy, blistering rash by coming into contact with these plants.

  • Whether working or just enjoying the outdoors, look out for these plants, and note the differences between each:
    • Poison ivy is generally found east of the Rocky Mountains, growing as vines or shrubs. The leaves can have either smooth or notched edges and are often clustered in groups of three.
    • Poison oak is more commonly found west of the Rockies, usually as a small bush but sometimes as a climbing vine. Its leaves are smooth-edged and cluster in groups of three, five, or seven.
    • Poison sumac is most often found in wet areas of the Southeast. The leaves are generally smooth and oval-shaped, with seven to 13 growing on each stem.
    • The appearance of each of these plants can vary considerably from region to region and with the seasons. Even dead plants in underbrush can transmit the toxic oil to the skin. Identification of these plants can help one avoid them.

Causes of Poison Ivy, Oak, and Sumac Rash

The rash caused by poison ivy, oak, and sumac is an allergic skin reaction to an oil called urushiol that is inside the plant. This oil is found in all parts of the plant, including the leaves, stems, roots, and berries.

Exposure to the oil occurs through any of the following:

  • Touching any part of the plants
  • Touching clothing or other objects that have contacted the plants
  • Touching pets or other animals that have contacted the plants
  • Exposure to the smoke of burning plants

Poison ivy, oak, and sumac rash itself is not contagious. However, if oil remains on the skin or on clothing that came in contact with the plants, and the oil comes into further contact with skin, a rash may result. The rash may appear to "spread" because it can develop over several days, or it's possible the oil was not entirely removed from all surfaces.

Risk factors for developing poison ivy, oak, or sumac rash include being in areas where the plants grow, engaging in outdoor activities, and coming into contact with them.

Medically Reviewed by a Doctor on 6/12/2015

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Patient Comments & Reviews

The eMedicineHealth doctors ask about Poison Ivy, Oak, and Sumac:

Poison Ivy, Oak, and Sumac - Remedies

What home remedies helped your poison ivy, oak, or sumac rash?

Poison Ivy Oak And Sumac - Symptoms

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Poison Ivy, Oak, and Sumac - Treatment

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Learn home remedies for the treatment of poison oak exposure.

Home Remedies and Other Treatments for Poison Oak Exposure

Author: Nili N. Alai, MD, FAAD
Editor: Jerry R. Balentine, DO, FACEP

Poison oak, also called western poison oak or Pacific poison oak, is one of the causes of allergic contagious dermatitis (ACD). Poison oak may appear as a dense shrub in open sunlight or as a woody vine under shadows. Similar to poison ivy, poison oak has three smaller leaflets on each leaf. Poison oak plants contain an oil called urushiol, a toxic chemical in their leaves, stems, and roots. Many people develop an allergic reactionthrough direct or indirect contact with urushiol or inhalation of urushiol smoke. The initial immune reaction begins once the poisonous substance is absorbed onto their skin or through mucous membranes like the nose or lips. Together with poison ivy, poison oak leads to 10% of lost work time in the U.S. Forest Service. Hundreds of firefighters in California's coastal ranges are so severely affected that they cannot work.

While about 15% of people may be immune to poison oak, this poisonous oil can cause serious allergic reactions in the majority of people.

Read What Your Physician is Reading on Medscape

Plant Poisoning, Toxiccodendron »

Toxicodendron dermatitis is an allergic contact dermatitis (allergic phytodermatitis) that occurs from exposure to members of the plant genus Toxicodendron.

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