Among such cytokine-receptor signaling cascades, α-melanocyte stimulating hormone (αMSH) and its receptor, melanocortin 1 receptor (MC1R), endothelin-1 (ET-1) and its receptor (Endothelin B receptor, ET-B) and stem cell factor (SCF) and its receptor (KIT), have been shown to substantially contribute to UVB-induced melanosis (Imokawa et al., 1992, , 1995, 1997; Lerner and McGuire, 1961; Bolognia et al. Here, MC1R is linked to freckles.