Resorcinols and catechols: a clinical study of cross-sensitivity

All allergic 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.

The purpose of this study was to determine the incidence of cross-sensitivity between these plant species.

Alkylresorcinols (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 microL (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.

No 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 naive when tested to homologous Philodendron resorcinols.

Patients who are sensitive to Philodendron species (or other resorcinol-containing plants) may not necessarily be cross-sensitive to Toxicodendron species and vice versa.