|Bob - are you sure it's an urushiol oil induced rash (aka poison ivy rash)? There are other possibilities. Could it be "Hot Tub Rash" (folliculitis)? This is caused by a microscopic germ.
I doubt that some poison ivy leaves in the hot tub would cause this problem. The chlorine would speed up the oxidation process of urushiol oil and render it harmless. Also, if these leaves were naturally shed by the plant then there is no urushiol oil in the leaves. Urushiol oil flows in the plant much like sap.
Hope this helps.