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.
Red, streaky, patchy rash where the plant touched the skin
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.