Allergic contact dermatitis (ACD) is a common inflammatory skin disease, which represents a major public health issue in industrialized countries. ACD is induced by repeated contact of individuals with environmental chemicals and is characterized by a delayed type IV hypersensitivity response with skin inflammation mediated by allergen-specific T cells in sensitized individuals. The current diagnosis is based on clinical examination, assessment of environmental exposures and patch testing. Although the robustness of patch tests has long been established, this method can sometimes give inconclusive results, leading to problems in disease management. Preliminary results indicate that the molecular analysis of Patch-Tests (PT) reactions could allow a more reliable diagnosis. Importantly, this gene profiling approach may help to identify patients with false positive PT reactions, i.e. patients whose PT reactions did not show any allergy signature. However, it remains to be demonstrated that the presence or absence of allergy biomarkers in PT lesions are indeed predictive of ACD response in patients. The main objective is to describe the correlation between these molecular signatures and the reactivity of individuals when they are exposed to allergenic compounds under conditions of use (using ROAT test).