Urushiol (a
ortho-di
phenol with a long
hydrocarbon chain) is an white/light yellow oil found mainly in the
Rhus genus of plant life. The
irritant in
Poison Oak,
Poison Ivy. Urushiol binds to the skin, and causes rashes to form in about 85% of all
humans. Frequent
exposure increases sensitivity.
Interestingly enough, Urushiol is also found in the shells of cashew nuts.