The brown and black form of melanin — the protective pigment that gives skin its darker tones and shields DNA from UV damage.Produced in melanocytes via the MC1R–cAMP–PKA–MITF–tyrosinase pathway. Eumelanin absorbs UV radiation and quenches reactive oxygen species generated by UV exposure, providing genuine photoprotection. Contrast with pheomelanin (red-yellow pigment, produced when MC1R signaling is low), which provides less UV protection and may actually generate reactive oxygen species under UV exposure. MC1R agonists specifically promote eumelanin synthesis — the pharmacologically relevant distinction for both EPP therapy and tanning applications.