Natural red hair color is primarily caused by variants in the MC1R (melanocortin 1 receptor) gene, which regulates melanin production in the body. These variants favor the production of reddish yellow pheomelanin over Martina Big Says She's Black From Melanotan II Injections Misinformation Red hair comes with a hidden biological advantage. Scientists have discovered that pheomelanin, the pigment responsible for red hair and fair skin in humans, as well as orange feathers in birds, may Reduced MC4R signaling alters nociceptive thresholds associated with red hair Science Advances