Skin lightening products form a major segment of cosmetic products worldwide and carry with them the promise of flawless skin free from age spots, blemishes and scars. Whatever the color of the skin, it is susceptible to damage due to environmental agents, physiological changes and psychological factors. The demand for “skin fairness products” is rooted in the need to eliminate localized hyperpigmentation as well as to lighten the general skin tone. Motives behind the use of skin lightening products vary considerably between cultures. In Western countries, people wish to eliminate or inhibit the development of irregular pigmentation including melasma (chloasma or localized discoloration), age spots (Lentigo senilis) or liver spots (associated with sun damage or aging sometimes appearing as raised spots or Seborrheic keratoses) and freckles (Lentigo aestiva). In Asia, a lighter skin color is associated with beauty and aristocracy. Therefore, in Asian countries, skin lightening products are used with the intent to lighten and brighten the skin tone.
Skin pigmentation is influenced by several factors, including hemoglobin in the blood vessels, carotenoids in the dermis and, particularly, the dark pigment, melanin in the epidermis. Two forms of melanin are produced in the epidermis: pheomelanin, which is red brown to yellow in color, and eumelanin which is dark brown to black. The relative proportions of these also influence skin color. In addition, individuals differ in the number and size of melanin particles. Melanin biosynthesis (melanogenesis) is influenced by genetics, environmental factors, diet and medication. The production of melanin by specialized cells called melanocytes (in the basal layer of the epidermis in light skinned people and in the basal as well as horny layer in dark skinned people) occurs through the action of the enzyme tyrosinase.