I use Fels Naptha bar laundry soap, after my friend's Grandmother pointed it out. You wet down the bar of soap, lather it on, and let it dry (do not rinse off). Every time the poison ivy starts to itch, you can use the wet bar of soap to somewhat safely scratch the spot (ok, I confess I don't think that's the intention, but well, I'm one of those compulsive poison ivy scratchers), and the soap dries out the area.
A poison ivy rash does *not* spread. That's a common misconception. The rash will break out where you first touched the plant, and will slowly break out to where the resin was also in contact with your skin. It looks like the rash is "spreading", but it's merely just appearing where you were already infected. Itching does not "spread" the rash. Itching can cause secondary bacterial infections, which are equally nasty.
Should your rash start to "weep", that is, leak semi-clear yellowish liquid from the spots where you've scratched, or even where you haven't scratched the rash, that's a good sign, because it means your case is actually progressing through its cycle. It's important to wash that weeping off with soap (regular or dish soap) and cool/cold water, and to keep your rash clean.
Aloe vera and vitamin E will help your skin heal, and you should not pick at scabs, but rather soften them with lotions.
Tom Brown's Guide to Wild and Medicinal Plants (1985, ISBN 0-425-10063-4) lists acorn tea, birch tea, bulrush, burdock, cattail, chicory, comfrey, hemlock, jewelweed, milkweed, mint, spicebush, sumac (staghorn, not poison obviously), sweet fern, thistle tea, and yucca. The guide is a fantastic and entertaining reference on how to use plants for a number of things, and I leave looking up each of these plants to you. (I also recommend any of the books by Tom Brown, Jr. He has an entire series of outdoor guides that are extremely informative and entertaining reading. I really enjoyed attending his Basic Tracking and Wilderness Survival course, though it was expensive.)
Someone once told me that if you take a knife, and deliberately scratch your rash until it's raw and then pour bleach over it, the rash will go away. I was never brave (or stupid) enough to try this. For some reason, I imagine it would scar and hurt really badly. I'd rather scratch than lose a limb. Check your home remedies with a couple of sources before trying them out. I do NOT recommend bleach (lots of readers keep pointing out that it's a Really Bad Idea); I recommend verifying home remedies before trying them.
A reader adds: "You would do well to mention on the home remedies page that temporary relief from the itching can be obtained by getting in the shower and holding your blisters in the stream while setting the water flow to the hottest temperature you can stand. I have been hyperallergic since 1948, and this is gives me more effective relief than anything else, including cortisone shots."
Another reader points out that Vitamin C powder, when mixed with water into a paste and applied, helps. The reference link is here (this link leaves my site), scan down a bit to get to the poison ivy information.
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