Who is affected by poison ivy, oak, or sumac rash?

Poison ivy, oak, and sumac are plants that can cause a skin rash called allergic contact dermatitis. The rash is caused by the oil (urushiol) found in these plants. Urushiol is an allergen, so the rash is actually an allergic reaction to the oil in poison ivy, oak, or sumac.

  • About 50% to 75% of people in the United States are allergic to poison ivy, oak, or sumac and will develop a rash.1, 2
  • About 10% to 15% of the U.S. population will not develop a rash after contact with any of these plants.2 These people are said to be tolerant.
  • About 10% to 15% of the U.S. population are extremely sensitive to the plants' urushiol and will have swelling, extreme blistering, fever, and a feeling of illness, usually within 2 to 6 hours after exposure.1 These people need to seek emergency medical care when they are exposed.
  • About 35% of the U.S. population will have no reaction to small amounts of urushiol but will react to high levels.1
  • Each year, up to 50 million people in the U.S. develop a rash caused by poison ivy, oak, or sumac.2

Who is likely to be sensitive to poison ivy, oak, or sumac?

  • People who are highly allergic to other allergens (such as pollen, animal fur, or dust mites) are somewhat less likely to be allergic to poison ivy, oak, or sumac.
  • Young people ages 8 to 14 are more likely to be allergic to the plants. Infants and young children up to about age 5 are not as likely to be allergic.2
  • If you reach adulthood having had no contact at all with urushiol, you have a significantly lower risk of becoming allergic to the plants.
  • It is never safe to assume you are tolerant to poison ivy, oak, or sumac, because your sensitivity to the plants can change at any time. You may become allergic, or you may have a more severe or less severe reaction to the plants.

Citations

  1. Anderson BE, Marks JG Jr (2007). Plant-induced dermatitis. In PS Auerbach, ed., Wilderness Medicine, 5th ed., pp. 1262–1286. Philadelphia: Mosby Elsevier.
  2. Gladman AC (2006). Toxicodendron dermatitis: Poison ivy, oak, and sumac. Wilderness and Environmental Medicine, 17(2): 120–128.

Last Updated: September 17, 2009

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