They are variable in appearance and habit, and despite its common name, it is not a "true" ivy (Hedera), but rather a member of the cashew and pistachio family (Anacardiaceae).

T. radicans is commonly eaten by many animals, and the seeds are consumed by birds, but poison ivy is most often thought of as an unwelcome weed.

[citation needed] Those affected can unknowingly spread the urushiol inside the house, on phones, door knobs, couches, counters, desks, and so on, thus in fact repeatedly coming into contact with poison ivy and extending the length of time of the rash.

[11] If plant material with urushiol is burned and the smoke then inhaled, this rash will appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty.

[16] Urushiol binds to the skin on contact where it causes severe itching that develops into reddish inflammation or uncoloured bumps, and then blistering.

These lesions may be treated with calamine lotion, Burow's solution compresses, dedicated commercial poison ivy itch creams, or baths to relieve discomfort,[17] though recent studies have shown some traditional medicines to be ineffective.

[18][19] Over-the-counter products to ease itching—or simply oatmeal baths and baking soda—are now recommended by dermatologists for the treatment of poison ivy.

[21][22][23][24] Others argue that prevention of lesions is easy if one practices effective washing, using plain soap, scrubbing with a washcloth, and rinsing three times within 2–8 hours of exposure.

[30] Similar reactions have been reported occasionally from contact with the related fragrant sumac (Rhus aromatica) and Japanese lacquer tree.