A recent study suggests that atopy is not commonly associated with psoriasis vulgaris, supporting the concept that Th2-mediated atopy protects against certain Th-1-mediated autoimmune pathologies such as psoriasis, in which we discussed the intervention of the proinflammatory cytokine axes TNF, IFN type 1, and IL-17 [14,26]. This evidence concerns the gene IL17A and psoriasis vulgaris.