Dealing with the itch from poison ivy can be very stressful. So many people each year have an allergic reaction several times during the poison ivy, oak & sumac season. Quick action is needed when you suspect you have come in contact with the Urushiol. Because Urushiol can penetrate the skin within minutes, there’s no time to waste if you know you’ve been exposed. “The earlier you cleanse the skin, the greater the chance that you can remove the Urushiol before it gets attached to the skin,” says Hon-Sum Ko, M.D., an allergist and immunologist with FDA’s Center for Drug Evaluation and Research. Cleansing may not stop the initial outbreak of the rash if more than 10 minutes has elapsed, but it can help prevent further spread.