Volta et al. reported that 15% of NCWS patients suffered from allergy to nickel, but they did not further characterize this subgroup of patients, neither posed the NCWS diagnosis by means the double-blind placebo controlled challenge (DBPCC), as recommended. In this study, the investigators evaluated 1) the frequency of Nickel allergy and Systemic Nickel allergy syndrome in NCWS patients, and 2) the clinical, serological, and histological characteristics of NCWS patients with contact dermatitis Nickel positive in comparison to NCWS patients without contact dermatitis.