Poison Ivy, Oak, and Sumac Dermatitis: What Is Known and What Is New?

Poison ivy, poison oak, and poison sumac are the most common causes of clinically diagnosed allergic contact dermatitis in North America. Approximately 50% to 75% of the US adult population is clinically sensitive to poison ivy, oak, and sumac. We reviewed the botany and history of these plants; urushiol chemistry and pathophysiology, clinical features, and the prevalence of allergic contact dermatitis caused by these plants; and current postexposure treatment and preventive methods, including ongoing investigations in the development of a vaccine (immunotherapy). Although extensive efforts have been made to develop therapies that prevent and treat contact dermatitis to these plants, there lacks an entirely effective method, besides complete avoidance. There is a need for a better therapy to definitively prevent allergic contact dermatitis to these plants.

Urushiol Patch Test Using the T.R.U.E. TEST System.

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. CONCLUSIONS: 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.