Tecnu always helped me.

Here is the write up...

"Take control of the outdoor itch that plagues you. Use TecnuŽ Outdoor Skin Cleanser after you have been outdoors to remove the rash causing oil, urushiol (oo-roo-she-all). Simply apply Tecnu to dry skin for two minutes and rinse with cool water or wipe off with a cloth. When used within 2-8 hours after exposure to the plants, Tecnu can remove urushiol oil before the rash begins. Once the rash has started, washing with Tecnu helps remove any free oil on skin allowing the natural healing process to begin without possible recontamination.

Urushiol oil can also spread from contaminated clothing, shoes, gloves, tools and pets. Since the oil does not evaporate, it can remain on these items for months or even years at a time. Use Tecnu to remove the oil and avoid a rash from secondary contact."

http://www.teclabsinc.com/product-categories.cfm?id=1E8FDCC1-F136-4EBF-EF2DA11F1E0BAEB8

Wal-Mart used to carry it and most drug stores will.
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