As one who has had a LOT of encounters with my old enemy, P. ivy, I thought
I'd add my experiences.
 
Washing with water won't help get the oil off.  You need a good strong
soap. The oil seems to act almost like pine sap on your skin, though
invisible and impossible to see or feel.  That is the way you "spread it if
you scratch it" --  you smear it around with your fingernails to new areas.
 
Doug and Harry, the sensitizing works wonderfully. When I was 13, I got a
really bad case on both legs...running down a steep hill covered with it to
rescue a little brother who had fallen...I had it for months. Mother took
me to the doctor, who said the effects of a "poison ivy shot" would be
little, and it was probably best at this point to let it run its course. .
.I'd likely now be immune for a long time, he said. I was. All sorts of
exposure had no effect on me.  Then, at age 28, I dug Pachysandra plants in
early spring before the P. ivy leaves had emerged in an area that I didn't
know was infested with poison ivy. Bad news. The desensitization had worn
off. I got it all over the insides of both arms above my gloves, where I
ran my arms under the plants to free the roots. Really bad case!  Again,
when it had run its course, I was immune for about ten years.
 
Now, my home remedy: Jewel Weed, of two species, Impatiens capensis or
Spotted Jewel Weed and Impatiens pallida, the Pale Jewelweed.  This is an
omnipresent woodland and woods verge plant, with thick, juicy, translucent,
water-filled stems with knobby joints; its roots are a bit like those of a
corn plants, and are reddish tinged. The leaves are oval and scalloped. The
flowers are the best identifier:  a lot like snap dragon flowers, they are
either orange and spotted (I. capensis) or yellow (I. pallida) and they
dangle from a slender stalk. The seed pods will fire seeds many feet away
when ripe and touched.  (Just as garden variety Impatiens, or
Touch-Ne-Nots, will do.)
 
How to use it?  Andy, Doug, take note:  it grows just about everywhere P.
ivy does. Prefers moist woodlands and stream banks. Get acquainted with it.
It is great stuff. When you are going into P. ivy situations, uproot a
plant, crush it, leaves, roots and all. Rub this crushed up mass on all
exposed skin. NO poison ivy rash will develop.  If you get into poison ivy
without it, find some  and rub it on after the fact. No poison ivy will
develop. If you get poison ivy, rub the stuff on the rash and it will stop
its progression and dry up. Several applications may be necessary,
depending on the severity of the case and how late in its progression you
catch it. One of my sons was so allergic, and so adept at finding P. ivy in
early spring or late fall when there were no leaves on it to identify it
and immersing himself in the stuff, that we took to squeezing the stuff in
mass quantities and freezing the juice in ice cube trays.
 
        The absolute proof of the effects (in my book, that is...our pediatrician
sneered and said the only effect I was likely to get was a rash from the
Jewelweed and to stop playing around with unfamiliar plants) was:  Richard
and I and our two boys took Walter Sage to a wooded stream area we knew was
rich in landshells, fossils and Unionidae all three, a treat for Walter's
birthday. (And there's my shell connection.) We used the Jewelweed
preventative in advance of our descent into this area, taking special care
on Mike, my P. ivy kid. He was wearing shorts, and we took turns rubbing
his legs with the soggy green mass of crushed jewelweed till he howled.  At
one point in the day's activities, he slid down a bank of poison ivy on his
rear.  The ONLY place he got a rash (and a BAD one) was on the backs of his
legs ABOVE the shorts line where the slide shoved his shorts legs up above
the jewelweed-protected skin to expose unprotected skin.  Two days later
there was a sharp line of demarcation between healthy skin and a blistering
poison ivy rash!
 
I have read of its use as a remedy for Athlete's Foot (not exactly a
shell-related hazard! Though I am sure Art can come up with a connection)
and that it has antifungal properties. Also, I have encountered it again
and again as an old Indian remedy. In fact, that is where I learned of
it...in despair at one of Mike's horrible cases, I said to me, what in the
heck did the Indians do? And I read up on the subject and tried it.
 
Bad news, Floridians. . .I don't think Jewelweed grows in Florida, though
it is common from Nova Scotia to Georgia and west to Oklahoma. I also don't
believe that it is found in the West and don't know about the
Plains...habitat may not be there in the case of the latter.
 
Lynn Scheu