Thesis (M.Sc. in Pharm.)--Chulalongkorn University, 2001

The in vivo efficacy and skin irritation potential of six commercially available brands of skin whitening products, three for face and three for body application, was evaluated in healthy female Thai volunteers. The first study was to compared the skin whitening efficacy of the three face products A, B and C with the control (non-treatment). Each of the 12 volunteers received the three face products on the separate areas of her left and right forearms twice daily for 12 weeks according to the repeated Latin square sequence. The melanin and erythema values of the treated and untreated areas were then weekly monitored in each subject using Mexameter MX 16(R). Product A contained 5% licorice extract, product B contained 0.001% mulberry root extract, 0.01% Scutellaria baicalensis extract and 0.3% capryloyl salicylic acid whereas product C contained 1% vitamin B3. The three products also contained some types of UV filters as sun screening agents. Products A, B and C were found to be equally effective in reducing the melanin content with a significant effect over the control (P < 0.05) observed at two weeks and afterwards. The three products also appeared to have some erythema-reducing property, which could be due to the UV-protective effect of the sun screening agents. The three body-whitening products E, F and G were then evaluated using the same protocol but different set of volunteers. Product E contained 8% lactic acid whereas product F contained 0.5% licorice extract and product G contained 1% vitamin B3 and 0.1% fruit extract. The same UV filters were also present in these products. The three body products were also found to be effective in reducing the melanin content over the control (P < 0.05) but the onset of significant whitening was somewhat longer (3-5 weeks). In addition, E, F and G did not show any significant erythema-reducing effect, yielding the erythema values similar to the control at all weeks (P > 0.05). This could be due to a more rigid control of subjects to avoid exposure to irritating sunlight during the study. In summary, all six brands of commercial whitening products evaluated here were effective in reducing the melanin content of the volunteers' skin. However, caution should be provided to consumers that the whitening effect was measured using a highly sensitive and specialized instrument. The effect was extremely difficult to detect by visual observation, which was also highly subjective.