Metal Allergy

The goal of this clinical trial is to collect environmental, bio-humoral, and clinical data derived from patients with allergic contact dermatitis (ACD) and systemic metal allergic syndromes related to the exposure to heavy metals, nanoparticles, and emergent contaminants and from healthy subjects. The main question it aims to answer is: are environmental, bio-humoral, and clinical data derived from patients with ACD and systemic metal allergic syndromes, related to the exposure to heavy metals, nanoparticles, and emergent contaminants, different from ones obtained by healthy subjects? Researchers will compare serum and urine concentration of heavy metals and nanoparticles, patch test to metals, within-breath analysis of oscillometry parameters, serum zonulin, and serum levels of protein oxidation products among patients with systemic allergic syndrome (1st study group), patients with ACD (2nd study group) and healthy subjects (3rd study group). Participants will undergo: * measurement of exposure to heavy metals and nanoparticles including nickel, cobalt, chromium, palladium, molybdenum, aluminium, and copper, through serum and urine measurement of concentration. * Patch test to before mentioned metals. * Within-breath analysis of oscillometry parameters. * Measurement of serum zonulin (related to gastro-intestinal exposure). * Measurement of serum levels of protein oxidation products (as markers of systemic oxidative stress).