In vivo nickel allergic contact dermatitis: human model for topical therapeutics

Techniques to determine efficacy of topical agents on allergic contact derm atitis (ACD) may benefit from refinement. The aim of this study was to deve lop an in vivo human model system for the bioengineering and visual quantif ication of the effect of topical agents on nickel ACD, and to correlate ACD parameters. 14 nickel patch-test-positive subjects were included in a plac ebo-controlled, double-blind study after a pre-screening procedure with a s tandard diagnostic patch test with nickel sulfate in 54 healthy human volun teers. 5% nickel sulfate in petrolatum in a Finn Chamber(R) was applied on forearm skin for 48 h to create a standardized dermatitis. Thereafter, the dermatitis was treated with a model topical agent and a placebo control whi le recording endpoint parameters daily for 10 days. Resolution was quantifi ed with 4 parameters: visual scoring (VS), transepidermal water loss (TEWL) (Tewameter), skin blood flow volume (BFV) (laser Doppler flowmeter), and s kin color (a* value) (Colorimeter). The model agent reduced cutaneous aller gic reactions, especially on day 8 to 10, in comparison with the placebo co ntrol. A highly significant linear relationship exists among all parameters , except between a* and BFV. This model may provide robust biometrics for d etermining the efficacy of topical therapeutics on experimentally induced A CD.