Jewelweed is listed as a medicinal plant because of its ability to releive the itch of poison ivy. Strange as it may seem, it often grows right alongside the plant for which it is an antidote. You pretty much just boil the plants in water to make a concentrated 'tea' that you then apply to the rash. I can vouch for the fact that this works. I haven't boiled down any myself, but our family doctor used to give it to patients as his 'secret poison ivy cure' back when my kids were very little. It is also reported to work as just the juice of the plant without boiling it down - you inadvertantly get into some poison ivy and you just crush some Jewelweed and rub it on the spot. Potter's Cyclopaedia says that it can also be boiled with lard to make a salve to relieve hemorrhoids, and that the raw juice of the plant will remove warts and corns and cure ringworm. In New England Rarities Discovered, and American herbal written in 1672, it was written that the colonists considered it a remedy for bruises.
It's a pretty plant that I've loved since I was a child, and despite its propensity to spread a bit too enthusiastically, I'll always allow it to grow here, especially as long as we still haven't managed to get rid of all of our poison ivy.
Impatiens pallida, the yellow flowered form, is also effective. At least around here, though, it seems less common. It is a larger plant and seems to have no problem growing in the sun, as we have several patches along the road that seem to do just fine.
This has to be one of the easiest medicinal plants there is since it grows often right next to the plant for which it is an antidote and requires no preparation for use, unless you want to have a supply on hand for winter, which is when I often get in trouble with poison ivy when I come in contact with the roots while clearing a new space for a garden. And yes, I'm ready for spring; enough winter already. And I've been planning several new garden beds and renovation for as soon as I can get out there and start working. The days are getting longer so it can't be too long yet, can it?