Plants from the Toxicodendron family are the most common cause of allergic contact dermatitis, and include poison ivy, poison oak and poison sumac. Coming into contact with these plants can cause a rash consisting of a linear, or streak-like, group of itchy blisters or bumps.
The chemicals released from the plants, called urushiols, cause the itchy rash. Urushiol can be carried on the fur of animals, garden tools, sports equipment and clothing. The smoke from burning Toxicodendron leaves can also carry urushiol, and can result in inflammation in the lungs if inhaled.
Patch testing is not necessary for Toxicodendron plants, since most people would have a positive test and the diagnosis is made clinically. Treatment involves avoidance of exposure to these plants, and the use of topical steroids to reduce the rash and itching.
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