ABSTRACT
Skin color has always been of concern to human beings, and both men and
women often desire to alter skin color for medical or cosmetic reasons. In
certain cultures, general body whitening and “porcelain white” skin are
desired, whereas in certain geographic areas of the world, it is the “tanned
look” that is preferred. Interestingly, the need to remove hyperpigmentation
and to reduce the visibility of age spots, freckles, or uneven skin color is univer-
sal, resulting in a worldwide need for safe and effective pigment-modulating
agents. Concerns of changes in skin color are also frequently raised for
medical reasons. Pigmentary disorders can be inherited (e.g., vitiligo, Waardenburg
syndrome), acquired (e.g., post-inflammatory pityriasis alba, idiophatic guttate
hypomelanosis, melasma), medication related (minocycline, bleomycin, busul-
fan, zidovudine), or transmitted through infection (e.g., tinea versicolor),
(reviewed in 1). Many methods have been proposed to alter skin color. For
example, tyrosinase inhibitors, hydroquinones, retinoids, and melanocyte cyto-
toxic agents are all used for depigmentation. However, the currently available
topical agents that are based on these mechanisms are sometimes disappointing,
and there is a need for more effective, safer, and less irritating depigmenting tech-
nologies (reviewed in 2). Skin darkening could be obtained through natural UV
exposure or artificial tanning devices. These, however, result in accelerated skin
aging and in increased incidence of skin cancer (e.g., 3-5). Alternative methods
for “sunless tanning” have evolved, such as the use of dihydroxyacetone or
topical synthetic melanins (e.g., reviewed in 6). Unfortunately, such products
might produce a “nonnatural” skin color, they only minimally protect the user
from UV irradiation (7), and they are ineffective when skin hydration is high
(8). Thus, products are needed that could enhance the natural pigment content
of the skin, leading to a desired skin color and to enhanced photoprotection,
without the need of UV exposure.
