To avoid skin rash, get the facts on poison ivy, oak and sumac.

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The rash caused by poison ivy, oak, and sumac is an immune reaction to an oil called urushiol that occurs in their sap. Here are some essential facts you should know about these plants and their oil:

  • The fact is poison ivy, oak and sumac grow almost exclusively in North America (lucky us!), but not in Hawaii or Alaska.
  • Increased carbon dioxide in the atmosphere due to climate change is making poison ivy plants grow bigger and produce an even more potent form of urushiol, according to recent research.
  • Not all people are sensitive to urushiol, but most are. And you may not start reacting until you’ve been exposed a few times. Never count on being immune.
  • Barrier creams such as Ivy Block can prevent urushiol from getting on your skin. Other products are supposed to help remove the oil soon after exposure, though there’s less evidence they’re effective.
  • Scratching the rash won’t cause it to spread, even if you break the blisters. But try not to scratch, since it can lead to infection.
  • Washing exposed areas with soap and lots of cool or lukewarm water (within 5 to 10 minutes, if possible) can prevent the reaction.
  • Urushiol can survive on clothes, shoes, golf clubs and garden tools for months, even years, and cause a reaction. Wear clean gloves when removing clothing and shoes. Wash clothes in strong detergent, and wipe off shoes.
  • If you think you’ve been exposed to the oil from poision ivy, oak or sumac, be careful when undressing. In particular, avoid touching your face or genitals.
  • The rash can’t be transmitted from person to person. By the time the rash appears, the urushiol is gone.
  • Pets don’t react to urushiol, but they can carry it on their fur and spread it to people. Bathe your pet, wearing gloves, if you think it has brushed against poison ivy, oak or sumac plants.

All parts of the plant can cause rashes, not just the leaves—even if the plant is dead. So wear heavy protective gloves and clothing when uprooting poison ivy, oak or sumac plants on your property. Burning these plants can vaporize urushiol, which, if inhaled, can cause severe lung damage. Don’t burn them.

Let them be: Learn to recognize the leaves and berries of these plants if they’re common in your area. Poison ivy and oak have the distinctive "leaves of three." And if you know they’re around, wear protective clothing when out in the woods or working in the yard.


Originally published in The University of California, Berkeley Wellness Letter (July 2011)

Publication Review By: the Editorial Staff at

Published: 22 Jun 2011

Last Modified: 12 Feb 2015