Topical pimecrolimus in the treatment of human allergic contact dermatitis

Background: Contact dermatitis is a common clinical problem, with prevalent sensitizers being cosmetics, metals, medicines, and plants. Plants of the Toxicodendron species cause allergic contact dermatitis (ACD) in 50% to 70% of the population. Pimecrolimus is an ascomycin macrolactam developed for the treatment of inflammatory skin diseases and approved by the US Food and Drug Administration for atopic dermatitis. There are studies supporting the effectiveness of macrolactams when administered before antigen challenge, but there are no studies describing the effectiveness of these drugs in the treatment of established human ACD. Objective: To investigate the effect of topical pimecrolimus in the treatment of Toxicodendron-induced ACD once rash is evident. Methods: Poison ivy tincture was applied to the bilateral anterior forearms of 12 subjects with Finn Chambers (Allerderm Diagnostic Products, Petaluma, CA). After dermatitis was evident, volunteers treated each arm twice daily with either 1% topical pimecrolimus cream or placebo in a blinded fashion. Outcomes measured were a dermatitis grading score and time to rash and itch resolution. Results: The median +/- SEM time for rash resolution was 16.55 +/- 1.59 days in the treatment group and 16.27 +/- 1.82 days in the placebo group (P = 0.601). The median time for itch resolution was 4.73 +/- 1.56 days in the treatment group and 4.91 +/- 1.59 days in the placebo group (P = 0.167). The average dermatitis score was 2.26 +/- 0.17 in the treatment group and 2.32 +/- 0.15 in the placebo group (P = 0.62). Conclusions: The application of topical pimecrolimus is ineffective in the treatment of ongoing Toxicodendron-induced ACD.