I don’t know about Poisen Sumac, but Poison Sumac is worse than poison ivy or poison oak.

In the U.S., it is listed under the Federal Noxious Weed Act of 1974, as amended (7 U.S.C. 2801 et seq.), as a "noxious weed". Most U.S. states list this plant in similar categories. It is considered one of the "U.S. Invasive Weeds" . In terms of its potential to cause urushiol-induced contact dermatitis, poison sumac is far more virulent than its relatives poison ivy and poison oak. According to some botanists, poison sumac (Toxicodendron vernix) is the most toxic plant species in the United States (Frankel, 1991).

The poison shows itself in painful and long continued swellings and eruptions.

Urushiol-induced contact dermatitis (also called Toxicodendron dermatitis and Rhus dermatitis) is the medical name given to allergic rashes produced by oil urushiol, which is contained in various plants, including the plants of the genus Toxicodendron (including poison ivy, poison oak, and poison Sumac), as well as other plants in the family Anacardiaceae (mango, Rengas tree, Burmese lacquer tree, India marking nut tree, and the shell of the cashew nut), and even unrelated plants such as Ginkgo biloba.

Symptoms of the rash include itching, inflammation, oozing, and in severe cases a burning sensation. The American Academy of Dermatology estimates that there are up to 50 million cases of urushiol-induced dermatitis annually in the United States alone, accounting for 10% of all lost-time injuries in the United States Forest Service. Poison oak is a significant problem in the rural western and southern U.S., while poison-ivy is most rampant in the eastern U.S. Dermatitis from poison sumac is less common, but just as problematic.

The rash takes one to two weeks to run its course, but normally does not leave scars. Severe cases will have small (1–2 mm) clear fluid-filled blisters on the skin. Pus-filled vesicles, containing a whitish fluid, may indicate a secondary infection. Most poison ivy rashes, without infections, will self-resolve within 14 days without treatment. Excessive scratching may result in secondary infection, commonly by staphylococcal and streptococcal species. These may require the use of antibiotics.