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European consumer exposure to cosmetic products, a framework for conducting population exposure assessments Part 2. European consumer exposure to cosmetic products, a framework for conducting population exposure assessments. Hall , S. Characterization and quantification of the skin radiance through new digital image analysis.

Definition of Cosmetics Stanley R. Milstein , Allen Halper , Linda B. Inter-instrumental variation of skin capacitance measured with the Corneometer. Good clinical practice.

Guidelines in dermocosmetic testing. Claim support: how to create and substantiate claims. Testing laboratory. Research staff. Testing population. Testing devices and methods. Factors influencing measurements. Study design. A baseline reading T 0 was taken followed by measurements at 30 T 1 , 90 T 2 and T 3 min after application of the aloe gel materials. During the long-term study, the aloe gel solutions were each applied twice daily i.

A baseline reading T 0 was taken, followed by measurements after 1 T 1 , 2 T 2 , 3 T 3 and 4 T 4 weeks after commencement of treatment. Measurements were performed h after the last treatment was applied in the evening prior to the day of measurements. The mean of three measurements are displayed in arbitrary units ranging from An increase in these parameter values indicates an increase in skin hydration.

The overall ability of the skin to return to its original shape is shown by Uf — Ua. R resilient distension is the residual deformation at the end of the measuring cycle. The closer the values of the R2- and R7-parameters are to unity i. The smaller the value of R6 is, the higher the skin elasticity becomes.

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The R8-parameter indicates a greater ability of the skin to return to its original state when its value is closer to that of the R value. The effect of the materials on skin erythema was performed according to the guidelines on sodium lauryl sulfate SLS exposure tests from the Standardization Group of the European Society of Contact Dermatitis.

A certain time period after the skin has been irritated is required before the first measurement can be performed. This prevented false readings due to the occlusive effect of the Finn Chambers and the initial hyperhydrating effect of SLS. The test materials i.

Thereafter, they were applied twice daily, in the morning and in the evening, for the rest of the study period. The second measurement T 2 was made on the 2 nd day following 1 day of treatment, and the final measurement T 3 was on the 7 th day following 6 days of treatment. Two different wavelengths are utilized to measure the absorption capacity of the skin when erythema is measured.

The one wavelength was chosen to avoid other color influences e. Results obtained were shown as indices on a scale from which will ensure that even the smallest changes in color were observed. For the test materials to be effective as anti-erythema agents, the hemoglobin content values should decrease after treatment T 2 and T 3. The effect of the test material are presented as percentage change as calculated by Equation 1 relative to the initial conditions T 0 and to untreated values T 0 untr and T n untr in terms of all the parameters measured in each part of the study.

Equation 2 was utilized in the erythema study. The basic method generally used for this type of design assumes independent data compound symmetry. However, given the dependence structure in the data, this assumption was violated. Therefore, mixed models were used to assess the influence of treatment and time on the various measures observed. Mixed model analysis allows a variety of variance-covariance structures,[ 31 ] in this study unstructured or first-order autoregressive AR 1 covariance structures were used.

Mixed models employ both fixed and random effects. Fixed effects such as treatment and time have levels that are of primary interest.

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Random effects such as subjects are not of primary interest. Statistical analysis for the erythema study was carried out using Microsoft Excel The Student t -test was performed to test for statistical significant differences between the different treatments and the different times. After lyophilisation of the precipitated ethanol insoluble gel materials, the average percentage yield obtained for A.

Aloverose acemannan , glucose and malic acid, which serve as marker molecules for identification of fresh A. Aloverose was not detected in the A. Aloe marlothii gel material caused a slightly higher hydration effect than A. Aloe ferox gel material showed a dehydrating effect negative percentage change over the short-term study.

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This dehydrating effect of A. Deionized water initially dehydrated the skin at 30 and 90 min after application, but showed a skin hydration effect at min after application. This increase in skin hydration min after application with deionized water was however less than that obtained with A. Aloe ferox gel material increased skin energy more than deionized water 30 and 90 min after application. Pairwise comparisons with a Bonferroni adjustment between the different treatments revealed a statistical significant difference between A.

The short-term hydrating effects of A. Skin entropy end homogeneity showed a statistical significant difference between A. A statistical significant difference existed between A. This indicates that A. From the single application study it was seen that after 1 h only the 0.

At 2 and 3 h after application, the 0. From this figure it can be seen that A. Aloe marlothii gel material dehydrated the skin the most of all the aloe materials investigated from week 1 to week 4. Aloe ferox gel material showed a 1. The dehydration effect caused by A. The placebo i.

The three aloe gel materials as well as the placebo increased the skin entropy [ Figure 6a ] slightly after the first week of treatment, with A. A decrease in skin entropy was observed after 2, 3 and 4 weeks of treatment with the A. Aloe vera gel material showed a small percentage increase in skin entropy after 2 weeks of treatment, thereafter also decreasing after 3 and 4 weeks of treatment.

The skin homogeneity almost followed the same pattern, except that initially A. An increase in skin energy was shown with all the aloe gel materials after the first week of treatment with A. Aloe vera and A. Aloe ferox gel material exhibited an increase in skin energy after 1 and 3 weeks, and a decrease in skin energy after 2 and 4 weeks of treatment.

However, none of these differences between the treatments were found to be statistically significant. Aloe marlothii gel material showed the largest negative effect on the skin's gross elasticity R2 when compared to the other aloes and the placebo. The R6-parameter [ Figure 7b ] measures the stretch capacity of the skin and negative values reflect improved skin condition.

Therefore, the R6-parameter correlates with the other R-parameters in showing that skin conditions did not improve. The only negative percentage change indicating improved skin conditions is after 1 week and 4 weeks of treatment with A. Interesting is that the placebo showed the highest percentage positive change, thus showing the least improvement of the R6-parameter.

The R7-parameter seen in Figure 7c showed a decrease in the elastic portion of the skin with the highest percentage decrease after 2 weeks of treatment. Negative values in R7 reflect a decrease in biological elasticity. Aloe marlothii proved to have the most negative effect on these parameters after 2, 3 and 4 weeks of treatment. Thus deionized water was statistically better than the aloes in improving skin hydration.

A previous study found that A. However, when the formulations were compared with each other after 2 weeks of application the formulation containing 0.

Practical Aspects of Cosmetic Testing How to Set up a Scientific Study in Skin Physiology

The findings of our study are different from the other studies described above, which may be ascribed to differences in the composition of the formulations tested pure aloe gel materials dissolved in water in this study versus formulations containing excipients in other studies , but also due to the difference in composition of the aloe gel from different species. The external use of aloe gel on intact skin is not associated with adverse reactions and is generally regarded as safe.

In the present study, two volunteers were withdrawn from the study due to severe allergic reactions.

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From weekly questionnaires it was determined that 11 The volunteers experienced a red rash, especially when the aloe gel started to dry on the skin, with either a burning or itching sensation. In the present study, the SLS exposure test was performed to compare the anti-erythema efficacy of the aloe gel materials to the positive control group hydrocortisone gel.

The percentage change in skin erythema as expressed by hemoglobin content from irritation T 1 to two time intervals T 2 and T 3 after treatment with test materials are given in Table 2. Percentage change in skin erythema hemoglobin from irritation T1 to two time intervals T2 and T3 after treatment. Hydrocortisone gel showed a