Outdoor Poison Oak And Ivy Skin Cleanser By TecnuSimply 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 re-contamination. 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.