An oil called urushiol causes skin irritation when you brush up against this 3-leafed plant, Rhus radicans
... Once you get the oil on clothing, it can sit for months and still cause a rash
... [DOC] [TLE] Poison Ivy - Keith Conover's Home Page [PAR] (Toxicodendron radicans, previously known as Rhus ... Urushiol is the oil in 
Poison Ivy bark ... plants, such as Poison Oak or Poison Sumac  to which ... Ivy 
leaf is actually a compound leaf with three separate leaflets .... Shelled cashew 
nuts themselves don't seem to cause allergy.