TNF and psoriasis: Using skin-lavage to extract biomarkers from the surface of skin, Portugal-Cohen et al. have shown clear differences in expression levels of skin hydrophilic biomarkers, including cytokines (IL-1α, TNF-α and IL-6) and antioxidants (uric acid, total antioxidant scavenging capacity), between lesional and non-lesional skin in patients with atopic dermatitis and psoriasis [7, 36].