Skin-whitening cosmetics is one category of advanced cosmetics and it decreases pigmentation (generally
known as blotch, freckle) of the skin caused by the solar ultraviolet (UV, wavelength in the range of 400 to
10 nm) rays. People, especially women, have always longed for skin that takes on a transparent impression—
being brightly white without blotch, dark brown spots, and being somber. Especially it is said that in Asia,
because the change of the color tone of the skin is considered a symptom of skin deterioration, people strongly
tend to desire a uniform skin color tone more than any other race. As regards the market target, Japan being the
center of research and development emphasizes the fact that it is Asia so far for skin-whitening cosmetics. But
since a major European–American cosmetic company has stressed the development of such products, development
and market competition has intensified. The largest primary determinant of human skin color is
melanin pigment produced by the melanocyte, which exists in the epidermal basal layer. Inside the melanocyte,
tyrosine, one of the amino acids, works as the substrate, producing the melanin pigment by the activation of the
enzyme tyrosinase. Melanogenesis progresses through the pathway shown in Figure 1.