CCL22 and inflammatory skin disease: Keratinocytes and their secreted chemokines, primarily CC chemokine ligands (CCLs), including CCL5 (RANTES) (Yang et al., 2018), CCL17 (TARC) (Werfel, 2009), CCL22 (macrophage-derived chemokine, MDC) (Lim et al., 2015), CCL27 (CTACK) (Kakinuma et al., 2003), and CXC chemokine ligand (CXCLs, such as CXCL8 (IL-8) (Mirandola et al., 2011), are regarded as triggers for the progression of skin inflammatory diseases by mediating the recruitment of immune cells into the inflammatory skin tissue (Homey et al., 2006; Sugaya, 2015).