The Trp-derivative FICZ was used as a potent AHR ligand in these studies of the role of AHR in skin barrier functions, but none of them discussed the production of FICZ by the commensal yeasts that colonize human skin (Magiatis et al., 2013) or presence of this ligand in the skin of patients with vitiligo and seborrheic dermatitis (Schallreuter et al., 2012; Magiatis et al., 2013). Here, AHR is linked to vitiligo.