| Yes it is true that the purple smoke bush is part of the same family as poison sumac. The family name is Anacardiaceae (common name cashew) and comprises 70 genera and 850 species of trees and shrubs but not all are poisonous. Here is a link to information about this plant family: Anacardiaceae plant family.
Your purple smoke bush is a member of the Cotinus genus. I did find a reference which stated that the "Cotinus coggygria" or Smoke-tree has urushiol. Here is an exerpt from a scientific paper on Cotinus coggygria:
Cotinus coggygria Scop.
(syns Cotinus coriaria Duhamel, Rhus cotinus L.)
Smoke Tree, Wig Tree, Venetian Sumach, Fustic Wood, Hungarian Yellow-wood
This species and its varieties are occasionally grown as ornamental shrubs for their brilliant leaf colouring in autumn (fall). The species occurs naturally from the Mediterranean to China.
The wood, when cut for veneers, and the sap have both been reported to cause dermatitis (Hausen 1970, Behl et al. 1966, Maiden 1909).
The yellow dye, young fustic, may be obtained from the wood (Willis 1973). The leaves were formerly used for tanning because of their high tannin content (Hurst 1942).
I have not found much online about sensitivity to the smoke bush and suspect that it is not as highly toxic as our more commonly known "friends" of poison ivy, oak, and sumac.
Anyone else know about this? | 
