The differences in skin color are the result of genetic background and environmental exposure to the sun [9-11]. Darker pigmented skin evolved in those whose ancestors lived near the equator [12]. It is widely believed that an increase in skin melanin protected the skin from the ultraviolet light exposure in equatorial locations. Lighter skin color may have developed to ensure sufficient vitamin D formation in the epidermis of persons living in northern latitudes [12,13].
Variations in skin color are not due to differences in the melanocyte number, but rather to the size, number, and grouping of melanosomes [14]. In general, dark-skinned subjects have an increased number of large individual melanosomes [15,16]. In these individuals, the melanosomes can be found throughout the epidermis. The melanosomes of lightskinned subjects are predominantly smaller with less melanin, and are found clustered together. In fair-skinned subjects few, if any, melanosomes are found in the upper epidermis. In people of Asian descent, melanosomes are relatively large and found individually, as well as grouped together [17].
Skin color is also affected by exposure to ultraviolet radiation [18-20]. Fitzpatrick developed the most commonly used skin color classification to correlate the amount of tanning or burning in light-skinned individuals in response to UV light [21]. Persons of color were added as three groups, Types IV, V, and VI, to the Fitzpatrick scale. Although widely used today, the Fitzpatrick system is not a good predictor of postinflammatory hyperpigmentation, or keloid scar formation in persons of color [22]. Newer skin-classification systems have been designed to give a better assessment of the risk of these side effects. The Lancer Ethnicity scale combines a person’s ancestry as well as skin color to determine their tolerance to cosmetic laser procedures [23]. Specific classifications have been developed for persons of African [24], as well as Hispanic heritage [25].