BACKGROUND: Poison ivy (toxicodendron) dermatitis is the most common allergic contact dermatitis in the USA. No studies have shown an effect of washing after a short period of time for the prevention of binding of urushiol to the skin. Objective To evaluate the efficacy of three different modes of postcontact prevention using a surfactant (Dial ultra dishwashing soap), an oil-removing compound (Goop), and chemical inactivation (a commercial product Tecnu). METHODS: A consented, unsponsored, volunteer experimental study on medical students from the University of Missouri School of Medicine, Kansas City. Each subject served as his/her own control, comparing four 2.5-cm exposed squares on the inner aspect of the forearm, three of which were treated and one untreated. RESULTS: Comparisons between the different agents were nonsignificant with P > 0.05. Each treatment, however, was significantly improved over the untreated control. CONCLUSIONS: Our study showed 70%, 61.8%, and 56. 4% protection with Tecnu, Goop, and Dial, respectively, when compared to the positive control, or to the possible maximum response, with a cost per ounce (in a local drug and automotive store) of $1.25, $0.07, and $0.07, respectively, for a decrease in protection that is nonsignificant.