The active ingredients in the oil of the Toxicodendron sp. (poison ivy,
oak, sumac) are a group of chemicals called urushiol.  This is inturn
composed of several catechols.  These are basically a benzene ring with
two hydroxyl groups (-OH) and a hydrocarbon chain.  The oil of and by
itself does not cause the rash.  It is a hapten.  These are substances
which are two small to trigger an allergic reaction but when they bind to
proteins in the skin can then trigger such a reaction.  Thus it is
imperative to wash the oil off when contact occurs.
 
I have heard anecdotal reports of the use of jewelweed.  One of them even
appeared as a letter to the editors of the New England Journal of Medicine
some years back.  I am not aware of any rigorous, controlled study of its'
effect.  There appears to be no ill effects of skin contact with the sap
of jewelweed that I know of and I have used it in the past.
 
When comparing the leaflets of the two plants those of poison ivy tend to
be somewhat triangular in shape.  They tend to be shiny and may have a
purplish hue.  The leaves of jewelweed tend to be more oblong, lighter in
color and lack the shiny appearance.
 
I trust that these observations add to those already posted.
 
Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History
Assistant Professor - Family Medicine
 
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