Resorcinols and catechols: A clinical study of cross-sensitivity

imageAllergic contact dermatitis caused by Philodendron species is common in the Hawaiian islands, and Toxicodendron species are the most common causes of plant-induced allergic contact dermatitis in North America. imageThe purpose of this study was to determine the incidence of cross-sensitivity between these plant species. imageAlkylresorcinols (pentadec[en]yl and heptadec[en]ylresorcinols) were isolated and purified from extracts of Hawaiian-grown Philodendron scandens subspecies scandens and Philodendron lacerum. Alkylcatechols (mixtures of pentadec[en]ylcatechols) from an extract of Toxicodendron radicans (poison ivy) were obtained from the Division of Biologics Standards (National Institutes of Health, Bethesda, MD). Seventeen patients from Hawaii and 8 patients from northern California were skin tested with 5 μL (concentrations, 1 to .001 mg/mL) of each allergen applied to the flexor forearm. The test sites remained open and were graded at 72, 96, and 144 hours. All 8 patients from California were naive to Philodendron species, and 8 patients from Hawaii were naive to Toxicodendron species. imageNo cross-reactivity occurred in patients who were Philodendron sensitive and Toxicodendron naive when tested to the homologous Toxicodendron catechols. Conversely, with one exception, no cross-reactivity occurred in patients who were Toxicodendron sensitive and Philodendron naive when tested to homologous Philodendron resorcinols. imagePatients who are sensitive to Philodrendron species (or other resorcinol-containing plants) may not necessarily be cross-sensitive to Toxicodendron species and vice versa.