The Establishment Of The Pigmentation Spot Model In Human Skin And Its Application For The Efficacy Assessment Of The Spot=removing And Whitening Products

Objective: By use of the artificial ultraviolet source to induce pigmentation in the healthy human skin, the author trys to build up a pigmentation spot model, and uses it for the efficacy assessment of the spot-removing and whitening products.Methods:Part I: The establishment of the pigmentation spot model in human skin for the efficacy assessment of the spot-removing and whitening cosmetics.Three groups of health volunteers were chosen as testees. Minimum erythema dose(MED) was measured at each testee's upper arms. According to the MED value, the three groups were exposed to ultraviolet irradiation (wavelength 290 nm - 400 nm) with adosages 1. 5 times MED, 2 times MED and 2. 5 times MED respectively at their upper arms. The erythema and pigmentation at the irradiated sites were evaluated before and after irradiation, and L , a , b , MI , and EI values were measured.Part II: Human test using above model for the efficacy assessment of the spot-removing and whitening cosmetics.Health adult volunteers were chosen for the study. Ultraviolet irradiation with a dose of 2MED at their upper arms were performed following the above-metioned method. Four samples, namely 0%, 3%, 5%, 8% concentration of Arbutin were used on the pigmentation spot by random. At 1, 2, 3, 4, 5 weeks after irradiation , the values of L , a , b , MI and EI were measured and analysed.Results:1.Irradiation with different UV doses produced different degrees of pigmentations. Compared with 2 or 2. 5 MED group, the strength and uniformity of the pigmentation is significantly weaker in 1. 5 MED group (p<0.05). Comparing with 1. 5 or 2 MED group, the 2.5 MED group has more wrinkles and peels on the irradiated sites. (p<0. 05).2. The ΔL, Δa, Δb, ΔM, ΔE values in each spot were well balanced and there were no difference among spots (p>0.1).3. Compared with 2 or 2. 5 MED group, the AL and AM values were significantly weaker (p<0. 01) in 1. 5 MED group. Compared with1.5 or 2 MED group, Δa and AE values were significantly higher in 2.5 MED group (p<0. 01).4. In the next 4 weeks after irradiation , Δa and ΔE values were decreasing and there were significant differences between weeks(p<0.01).5. In the next 3 weeks after irradiation ,ΔL values was decreasing and there were significant differences between weeks (p<0.01) .6. The result of the efficacy test of different samples is as follows: the sample with 8% arbutin made the AL value of the spot going down significantly at the first week comparing with nagetive control (0% arbutin) and the sample with 3% arbutin (p<0. 05). At the third week, the AL value in sample with 8% arbutin was significantly lower than that of the samples with 0% and 3% arbutin (p<0.05).Conclusions:1. Single UV irradiation of 2 MED produced the better pigmentation and less skin wrinkles and peels, which may be the best dose for the establishment of pigmentation model.2. The erythma observed by eyes could reach its peak at 24 hour after irradiation , fade away gradually and disappear principally in the first week. However, Δa and ΔE values which was thought to present erythema in literature still show decreases...