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

Techniques to determine efficacy of topical agents on allergic contact dermatitis (ACD) may benefit from refinement. The aim of this study was to develop an in vivo human model system for the bioengineering and visual quantification of the effect of topical agents on nickel ACD, and to correlate ACD parameters. 14 nickel patch-test-positive subjects were included in a placebo-controlled, double-blind study after a pre-screening procedure with a standard diagnostic patch test with nickel sulfate in 54 healthy human volunteers. 5% nickel sulfate in petrolatum in a Finn Chamber 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 while recording endpoint parameters daily for 10 days. Resolution was quantified with 4 parameters: visual scoring (VS), transepidermal water loss (TEWL) (Tewameter), skin blood flow volume (BFV) (laser Doppler flowmeter), and skin color (a* value) (Colorimeter). The model agent reduced cutaneous allergic reactions, especially on day 8 to 10, in comparison with the placebo control. A highly significant linear relationship exists among all parameters, except between a* and BFV. This model may provide robust biometrics for determining the efficacy of topical therapeutics on experimentally induced ACD.