REFERENCEZanfel™ is a soap mixture of ethoxylate and sodium lauroyl sarcosinate surfactants. When "activated" (worked into a paste that can be spread effectively on the skin), the soap is able to bind urushiol and thus allow it to be removed from the skin by rinsing.
Zanfel™ is unique with respect to poison ivy/oak/sumac remedies in that it is supposed to remove resin from the skin after the rash has appeared. In one study, this effect was present even at 144 hours post exposure. However, it seems logical that at some point post exposure, urushiol is no longer present in the skin and that the allergic contact dermatitis (manifested as redness, itching, swelling, and blisters), would not be lessened by Zanfel™, unless it has some direct anti-inflammatory properties
Leaves of Three, Let Them Be: If Only It Were That Easy; Medscape Article, May 28, 2004; Patricia L Jackson Allen, MS, RN, PNP, FAAN