seven-year itch

"Horace K. Sawyer" wrote:

>  We
> >found a nice spot and I set up camp while the kids foraged for kindling and
> >swung from tree vines. I soon discovered a certain plant that instantly
> >burns your skin and feels like fire ant bites.  A little water relieved this
> >pain.  My son soon found this plant also.
>
>         What is this plant, anyone know?
>
> HK