The rash and blisters of Poison Ivy, Oak and Sumac are all caused by a chemical called Urushiol. Symptoms will persist until the Urushiol is completely removed from the skin. Ivy Dry Scrub "washes off" Urushiol from the skin shortly after initial exposure to prevent the itching, burning and blistering reaction. Ivy-Dry Scrub is a detergent-based product with patented Zyrtrel, plus Aloe Vera and Vitamin E to promote healing. Removes Urushiol from Poison Ivy, Poison Sumac, Poison Oak and related plants.