Poison ivy, poison oak, and poison sumac are the most common causes of allergic contact dermatitis in North America. Although extensive efforts have been made to develop therapies that prevent and treat allergic contact dermatitis to these plants, there lacks an entirely effective method, besides complete avoidance. Efforts to develop a more effective preventive therapy, such as a vaccine, are ongoing. To accurately evaluate the efficacy of these new therapies, an appropriate assessment tool is needed.
The aim of this study was to evaluate the safety and appropriate doses of urushiol required for a patch test based on the hydrogel delivery system of the Thin-Layer Rapid Use Epicutaneous Patch Test.
Nine subjects were patch tested with various doses of urushiol and a negative control on day 0. Patch test sites were inspected for any local reaction on days 2, 4, 7, 14, and 21 after the initial exposure and graded by standard morphology.
All 9 subjects did not have any significant adverse effects. The urushiol patch test using the hydrogel delivery method demonstrated urushiol sensitivity. All doses of urushiol resulted in a local reaction, and severity of reactions was correlated with dosage of urushiol used in the patch test.
From the *Penn State College of Medicine, Hershey;
†Department of Dermatology, Penn State Hershey Medical Center;
‡National Center for Natural Products Research and
§Department of Pharmaceutics and Drug Delivery, University of Mississippi; and
∥ElSohly Laboratories, Incorporated, Oxford, MS;
¶Hapten Sciences, Memphis, TN; and
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Sources of support (including pharmaceutical and industry support): Hapten Sciences, Inc, Memphis, TN. Penn State College of Medicine received funding to conduct the clinical study.
J.G.M. is a consultant to Hapten Sciences, Inc. The other authors have no funding or conflicts of interest to declare.