North American Fruit Explorers mailing list at ibiblio

[Lucky Pittman <lucky.pittman@murraystate.edu>]

At 10:47 AM 4/27/2007, Doc L. wrote:
> I have also heard that the Native Americans fed their children
> poison ivy leaves to develop an immunity tolerance to it. (sic!)

It's true.
Now, whether or not they knowingly/intentionally did this or whether 
it was just part of their culture, is another matter.
In the book, "It Will Live Forever", a tome on traditional Yosemite 
acorn preparation, Julia Parker indicated that the Paiute/Yosemite 
women often wrapped balls of acorn meal in poison ivy/oak 
leaves.  This would certainly have resulted in exposure to urushiol 
via an oral route, which could - and probably did - provide them with 
'oral tolerance' , an immunologic phenomenon in which if one is 
exposed to a potential allergen via an oral route - at an early age - 
one's immune system is less likely to respond adversely/excessively, 
as may be the case when exposed via a transcutaneous route.
It's almost as if the oral exposure causes the immune system to look 
at that allergen/antigen as 'normal', and possibly even as 'self'.

Lucky