Depends what you mean by "Lore". Most native folklore was in the form of an oral tradition, and as such we lost way more than we've saved.

Jacques Rousseau, in Études ethnobotaniques Québécoises (1945), says that when there was "too much water in the blood" the Mohawks of Kahnawakhe (Caughnawaga) would add some crushed poison ivy to a poultice of buttercup and cover it with a pierced animal skin to induce bleeding and to "express excess water".

re:

"Quand il y a trop d'eau dans le sang", fragmenter la plante, y ajouter quelques morceaux d'herbe à puce (Rhus radîcans), et après avoir appliqué sur le patient une peau trouée d'animal y déposer le mélange humecté d'eau froide. Il se forme une plaie par où s'écoule le surplus d'eau du sang."

He also claims that they also used it as a vesicant, as did the Potawatomi and the Meskwaki of the Great Lakes area.

link:

http://www2.ville.montreal.qc.ca/jardin/archives/rousseau/publi/Etudes_ethnobotaniques_quebecoises.pdf

Also, the Ojibway knew of it and its effects, but had no use for it, (Huron H. Smith, 1932, Ethnobotany of the Ojibwe Indians).

Now, a lot of the "lore" surrounding the ethnobotanical uses of Poison Ivy has come under scrutiny and is suspect, according to Senchina (2006) (http://www.bioone.org/doi/abs/10.3119/0035-4902(2006)108%5B203%3AEOPIPO%5D2.0.CO%3B2) (behind paywall - abstract available)