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 oils (resin) of these plants. Smoke from burning these plants can cause the same reaction. The oils usually enter the skin rapidly. It is rarely spread from person to person.
The rash does not spread by the fluid from the blisters. Therefore, once a person has washed the oil completely off the skin, the rash is usually not contagious.
Keep in mind that the plant oils may remain for a long time on contaminated clothing, pets, tools, shoes, and other surfaces. These contaminated items can cause rashes in the future if they are not properly cleaned.
The reaction can vary from mild to severe. In rare cases, the person is admitted to a hospital. The worst symptoms are often seen during days 4 to 7. The rash may last for 1 to 3 weeks.
Call 911 or go to an emergency room if:
Call your provider if:
Other steps include:
Anderson BE, Marks JG Jr. Plant-induced dermatitis. In: Auerbach PS, ed. Wilderness Medicine. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2007:chap 57.
Cydulka RK, Garber B. Dermatologic presentations. In: Marx JA, ed. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 118.
Habif TP. Contact dermatitis and patch testing. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 4.
Updated by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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