There is usually no scarring, but on occasion there can be secondary bacterial infection of the rash, requiring antibiotics. The widespread myth is that the blister fluid spreads the rash. That fluid is just a product of the allergic response. What can spread the rash is re-exposure to the resin from clothing, tools, or even pets that may have been contaminated. It takes three weeks to evaporate off these carriers.
Prevention is best.
If you don t touch it, you won t break out. Second, if you do get exposed, wash with soap and water within the hour. Kerosene and gasoline probably work, but seem a bit harsh when good old soap and water will do. Wash several times for good measure, as the resin can be hard to get off. Finally, when the plant is growing near your home, get rid of it.