. . and cause a rash, but they are not generally found packaged as a spice.
The berries are probably not intensely flavored and are eaten by birds and other animals. The toxin actually triggers an alergy in humans that most animals are immune to.
Poison Ivy is related to Cashews (parts are highly toxic), Mangos (not generally toxic) and Sumac. The berries of some Near Eastern varieties of sumac are used as a souring agent similar to lemon but American varieties contain the alergin.