Abstract:

The stimulation to melanosomes from ultraviolet （UV） irradiation in sunlight plays a crucial role in the formation of skin pigmentation and color spots. The current practice of anti-freckle and skin-whitening efficacy evaluation in our country basically lies in reducing the pigmentation that have been formed, which is unable to assess the influence of cosmetics on the melanin formation. In this study, a new human efficacy evaluation method was established to assess the effectiveness of cosmetics on inhibiting melanin production and blocking melanin transport. Based on the photobiological reaction mechanism of skin tanning, the influences of body regions and UV irradiation doses on skin pigmentation were investigated during the establishment and optimization of the anti-tanning model. The test areas on the skin were induced by single UV irradiation with 2 fold minimal erythema dose （MED）. The test products were applied for 9 consecutive days immediately after UV irradiation. The skin color （shown as individual type angle, ITA°） and melanin index （MI） were recorded on the day 0 （before irradiation）, day 5, day 7, and day 10. This method is successfully applied in the cosmetic anti-freckle and skin-whitening efficacy evaluation. Compared with the existing evaluation methods in China, this method is able to effectively evaluate the anti-tanning efficacy of the anti-freckle and skin-whitening cosmetics with shorter test period and lower cost.

Key words: melanin inhibition, evaluation model, anti-tanning efficacy evaluation, an exploratory approach