Skin Lightening Agents

1) AHA's

Alpha hydroxy acids (AHA's) work mainly as an exfoliant. Exfoliants are compounds able to slough away the top layer of dead epidermis cells of the skin, thereby leaving the skin appear smoother, fresher and less wrinkled. The result of exfoliation is to promote blood circulation in the skin and to increase the turnover of surface skin cells.They cause the cells of the epidermis to become "unglued" allowing the dead skin cells to slough off, making room for regrowth of new skin. AHA's may even stimulate the production of collagen and elastin, and are reported to improve wrinkling, roughness, and mottled pigmentation of photo damaged skin after months of daily application.The most common alpha hydroxy acids are lactic acid and glycolic acid. These two acids in particular penetrate the skin very well and are often used in skin care products. For centuries, alpha hydroxyacids have been one of the most commonly utilized peeling agents used to treat dry skin, acne, actinic damage and to improve skin color/texture. At low concentrations AHAs promotes exfoliation by decreasing corneocyte cohesion and stimulating new growth in the basal layer, while at higher concentrations AHAs promote epidermolysis and dispersed basal layer melanin. Lactic acid and glycolic acid are AHAs derived from sour milk and sugarcane juice, respectively. Alpha-hydroxy acids have been shown to lighten melasma, solar lentigines, and postinflammatory hyperpigmentation. Glycolic acid which acts as exfoliant, due to its easy penatration, it is used as an ingredient in skin-lightening products to increase the efficacy of other lightening agents such as hydroquinone by removal of the epidermis, thus enhancing the penetration of hydroquinone

2) Arbutin 

Arbutin is a molecule extracted from the bearberry plant that has found to have skin lightening properties. It prevents the formation of melanin and was effective in the topical treatment of various cutaneous hyperpigmentations characterized by hyperactive melanocyte function. Structurally related to hydroquinone, arbutin is a glycoside; a glycosylated derivative of hydroquinone inhibits tyrosinase activity competitively. Arbutin is a relatively simple chemical, with a glucose attached to a hydroquinone. Both hydroquinone and arbutin have skin lightening properties, primarily because they inhibit synthesis of melanin. But the glucose residue makes a difference: arbutin does not have the side effects that hydroquinone seems to have. Arbutin also has anti-cancer activity on melanoma cells.