Furthermore, Malassezia in the skin can metabolize to produce oleic acid (61) and the amount of oleic acid in the lesional skin of patients with psoriasis correlates with a reduction in IL-17 driver signatures following T cell activation (62), suggesting that skin micro ecological dysregulation compromises the skin barrier and alters skin composition, which in turn affects local immune function and promotes the development of psoriatic lesions. This evidence concerns the gene IL17A and psoriasis.