Poison ivy, poison oak, and poison sumac are three plants notorious for causing itchy, uncomfortable rashes that can turn a pleasant outdoor experience into a nightmare.

But poison oak may have more than three leaves, and depending on the season, species and local environment, plants can vary. All parts of the plant, including roots, can cause an allergic reaction ...

Poison sumac is considered more allergenic than poison ivy and poison oak, which are other well-known plants in the Toxicodendron genus of the sumac family. Poison sumac releases an oil known as ...