In Japan, the level of ultraviolet light protection efficacy for sunscreen products is indicated as SPF values and PA labeling. These indicators and test methods are not national standards but industry standards established by the Japan Cosmetic Industry Association (JCIA). This article reviews updated Japanese and global test methods and labeling standards, including PA++++ labeling which this year is being introduced to indicate the highest UVA protection efficacy for sunscreens in Japan.

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Collagen fibers in the dermis consist of type I and type III collagen, and the ratio of type III/I collagen decreases with aging. This is thought to affect the physical properties of the dermis. Collagen molecules are synthesized and secreted as pro-collagen by dermal fibroblasts. Then their N- and C-propeptides are cleaved by enzymes. Consequently, collagen molecules are engaged with each other and form collagen fibers. To elucidate the reduction mechanism of the type III/I collagen ratio in collagen fibers with aging, we investigated the age-related change in type I and type III collagen propeptide cleavage enzymes. Moreover, we examined the effect of dipotassium bryonolyl succinate on meprin, a type III collagen propeptide cleavage enzyme. As a result, mRNA expression of meprin reduced with aging more significantly than BMP-1 and ADAMTS-14, type I collagen propeptide cleavage enzymes. Meprin mRNA expression was increased by dipotassium bryonolyl succinate. On the basis of these results, it was concluded that the more significant decrease of type III collagen propeptide cleavage enzyme was a cause of the decrease in the type III/I collagen ratio in collagen fibers. Since dipotassium bryonolyl succinate enhanced meprin mRNA level, it may prevent and improve age-related change in dermal physical properties to control the ratio of type III/I collagen by preventing the reduction of meprin with aging.

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Sensitive skin is often accompanied by sensory discomforts such as burning, stinging and itching. Although the stratum corneum barrier malfunction is thought of as one of the reasons for sensitive skin, details of the malfunction of the stratum corneum have not been clarified in sensitive skin. In order to clarify this malfunction, we tried to visualize the stratum corneum barrier function using fluorescein, which is commonly used in the diagnosis of dry eye. We applied a solution containing the sodium salt of fluorescein on the skin surface and observed the skin with a fluorescence videomicroscope. The barrier disruption of inner arms with oleic acid enhanced the permeation of fluorescein into the stratum corneum. Moreover, the fluorescent intensity of the image correlated with the value of transepidermal water loss (TEWL).These results suggested that this novel technique visualized the stratum corneum barrier function precisely. Using this technique, the fluorescent image of sensitive skin indicated the disruption of the barrier function for the stratum corneum especially around facial pores. Furthermore, we succeed in visualizing the repair of the skin barrier function by the daily use of skincare products.

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We observed finishing of cosmetic foundation every day on the same skin to investigate the day-to-day variations in finishing which are often felt by many foundation users. We hypothesized that the adhesion of foundation to the skin varied every day because of daily changes in some conditions on the surface of the skin to which the foundation is applied. Therefore, 15 women in their 30s using a powder-type foundation were used as volunteers. We observed their finishing and determined the condition of their bare skin surface every day for 1 month. The items of determination for the skin were moisture content, sebum and elasticity, and the items given an observation score were scaling, acne, pores and color unevenness. As a result, we found that foundation finishing varied day to day for each subject even when they used the same foundation every day. The types of variation were categorized as “dry-appearance” and “uneven-appearance”. Bare skin condition also varied day to day. Correlation analysis between variation of foundation finishing and variation of bare skin condition with respect to each subject showed that “dry-appearance” variation correlated to changing scaling and/or acne on skin surface in plural persons. It is supposed that daily variations of asperity on the skin surface affect the adhesion of foundation to the skin, and enhance “dry-appearance”.

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At the outermost layer of cuticle, fatty acids [mainly 18-methyleicosanoic acid (18-MEA)] are connected with fibrous protein under these acids. This layer is called the F-layer. The F-layer allows the hair surface to be hydrophobic and have a good smoothness under normal conditions. After the F-layer is broken, the hairs lose 18-MEA from the surface, leading to the hydrophilization of the hair surface and the deterioration of the protective-barrier function against outside stresses, resulting in the hair surface developing an uncomfortable friction and rough texture. For keeping the healthy and beautiful hair, the lost F-layer need to be recovered with some cosmetic materials. We have developed Cetearamidoethyl diethonium hydrolyzed protein (CDHP), an ionic complex material consisting of rice peptide and aliphatic cationic compounds. This compound was designed by focusing on the F-layer structure. CDHP has simulated the F-layer structure of which the alkyl and peptide moieties correspond to 18-MEA and the protein parts of healthy hair surface, respectively. We previously investigated the properties of CDHP against damaged hair using fluorescence microscope observation. This observation revealed that CDHP selectively adsorbs to the damaged part of the hair surface. In this study, to investigate the physical character changes to the hair surface that occur with CDHP adsorption, we evaluated contact angle and frictional measurements of hair surfaces. These analyses revealed that CDHP restores the deteriorated physicochemical properties to the state of healthy hair. Furthermore, we found, with combing tests and sensory evaluation, that silicone-free hair conditioner containing CDHP improved hair texture significantly and maintained a good sensory character, respectively, over the long term.

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