Freckles can be related to a dominant receptor gene for melanocortin-1, but they can also be the result of skin that is more sensitive to light. The skin cells that produce the pigment melanin are called melanocytes. They will produce melanin to protect the skin from sun damage, and when that pigment is transferred to the cells that make up the outer layer of skin, it shows as freckles.
Anyone can have freckles regardless of their genetic background, but the degree of freckles appearing on the face, shoulders and chest is hereditary. Although they are not a skin disorder, individuals who have them usually possess a lesser degree of the protective pigment melanin and should avoid overexposure to UV ultraviolet radiation.