Ted (Bangkok, Thailand) on 01/04/2007:

The toxin resinous oil called Urushiol, can actually be detoxified by several ways. With the resins you can remove, or neutralize it nevertheless.
First start simple and wash the effected area with a strong detergent to remove the resin. When it is removed and the rash, is no longer reducing, you go to the next step of removing which is vinegar which will remove the other part of the resins.
How it is done is to grab a towel and try dabbing several times with vinegar, for example, to remove the resins. Try different areas of the towels that are clean and keep repeating until they are all removed. What vinegar does is it detox it and remove the oil. Rubbing alcohol will also work but less effectively than a vinegar.
Finally, after this is done several times, get the 3% hydrogen peroxide. It must not be weaker than 3% otherwise it will not neutralize the by oxidation of the resins.
The peroxide will cause drying, but it will also dry out whatever resins left over. So with a towel, this is rubbed with a 3% hydrogen peroxide several times, and find a new clean area of towel and do it repeatedly. The peroxide will neutralize what is left.
Finally, when it is done about 5-10 times, we apply this with lavender oil, 2-3 times liberally so that the oil will neutralize the toxin resin. Peppermint oil might further reduce but not necessary unless it is still irritating what is left of the rash and most resin at this stage should be removed.
The secret I think lies in the number of applications for it to work, which must be done for half a day, at one hour apart, at least. The reason why some antidote don't work is improper understanding of the mechanics of resinous oils on the skin.
Ted (Bangkok, Thailand) on 03/01/2004:

Oh by the way, a traditional remedy for poison ivy is jewel weed (touch me not), but it is not easy to get, this is why a vinegar, alcohol, detergent, and lavender are a bit easier to find, and hence the remedy are geared on convenience.
Also, Ordinary vinegar works the best. Most supermarket vinegar will work. An antidote for jellyfish poisoning is vinegar, but then it is also antidote for toxic alcohol (methanol), aspartame, splenda, etc. Vinegar works by detoxification and it is in fact actually anti-histamine, anti-inflammatory, to most toxic oils. That I found out quite by trial and error.