I didnt read to see if anyone else posted this, but... meatwad, use Mineral Spirits. It along with another chemical are the ONLY substance that can kill (dry out) the poison ivy once its one your skin. I had it about a week ago for only two days and i had it somewhat bad. This has also worked every time i have gotten it.
This is what i do
When it was itchy, i would scratch it until it was opened to relieve the itch. Then i would go and pour mineral spirits onto a paper towl so it was wet. Then i would rub the paper towl over the entire area that i had poison ivy. I would pour some more on the paper towl and do every other spot. I would only be itchy after waking from sleep. However, after 5 minutes of application, the itch was no longer there either and i didnt have to apply it until the next day. Now if it gets rubbed during the day alot you might need to reapply it later in the day.
Today i also touched a poison ivy leaf on accident while picking berries and i went in and washed my hands then went out and put some mineral spirits on it to kill any oil that might have been left on my skin.
It really does the trick.
edit: i just read the thread and some mentioned about sensitive skin. With mineral spirits, there is no burning or nothing. It just feels a little greasy for all of maybe three minutes until it dries completely.