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Poison Ivy, Oak, or Sumac - Topic Overview

What are poison ivy, oak, and sumac?

Poison ivy, oak, and sumac are plants that can cause a red, itchy rash called allergic contact dermatitiscamera.gif. It is the most common skin problem caused by contact with plants.

What causes a poison ivy, oak, or sumac rash?

The rash is caused by contact with a sticky oil called urushiol (say "yoo-ROO-shee-all") found in poison ivy, oak, or sumac. You can get the rash from:

  • Touching or brushing against any part of these plants, including the leaves, stems, flowers, berries, and roots, even if the plant is dead.
  • Touching anything that has come in contact with these plants, such as clothing, sporting gear, gardening tools, or pet fur.

The rash is only spread through the oil. You can't catch a rash from someone else by touching the blister fluid.

The rash is an allergic reaction to the oil. You become allergic to it through contact. After you have come in contact with these plants, your immune system may start to react to the oil as though it's a harmful substance.

What are the symptoms?

The usual symptoms of the rash are:

  • Itching.
  • Red streaks or general redness where the plant brushed against the skin.
  • Small bumps or larger raised areas (hives).
  • Blisters that may leak fluid.

Some people are very allergic to the oil. In these people, even a little bit of the oil may cause serious symptoms such as:

  • Swelling of the face, mouth, neck, or genitals. The eyelids may swell shut.
  • Widespread, large blisters that ooze a lot of fluid.

The rash usually takes more than a week to show up the first time you have a reaction to the oil. It develops in a day or two on later contacts. The rash may form in new areas over several days, but you will only get a rash where the oil touched your skin.

The rash usually lasts about 10 days to 3 weeks. But it may last up to 6 weeks in more severe cases.

How is the rash diagnosed?

A doctor can usually diagnose the rash by looking at it and asking questions about:

  • When you were exposed to the plant.
  • How long it took the rash to develop.
  • Other rashes you have had.
  • Your outdoor activities, work, and hobbies.

How is it treated?

If you get a mild rash, you can take care of it at home.

  • Apply a wet cloth, or soak the area in cool water.
  • Use calamine lotion to help relieve itching.
  • Try not to scratch the rash. Scratching could cause a skin infection.

Do not use the following medicines. They can cause allergy problems of their own:

  • Antihistamines applied to the skin (topical), such as diphenhydramine (found in Benadryl cream, spray, or gel).
  • Topical anesthetics that contain benzocaine (such as Lanacane).
  • Topical antibiotics that contain neomycin (such as Neosporin).

See your doctor if the rash covers a large area of your body or your symptoms are severe. A doctor may prescribe a corticosteroid cream to help clear up the rash. A severe rash may be treated with corticosteroid pills or shots.

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WebMD Medical Reference from Healthwise

Last Updated: February 19, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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