Recently along with the diversified lifestyles and environmental changes of consumers, there has been an increasing awareness on the importance of grooming and maintaining good health. Since 2020, the COVID-19 epidemic has caused changes in awareness and behavior, such as more careful skin and hair care, due to the increase in the time spent at home. Especially in the hair care industry, the market for high-end hair care products and treatments including out-bath treatments is growing. We speculate that these trends are brought about by the behavior change in young people from the digital communication measures centered on social media platforms. While the end of life with a mask is still uncertain, the beauty of hair, which is not covered by a mask, rather than the face, comes to be seen as a major factor that affects the impression of the person and it is expected that the trend to emphasize hair care will increase more than ever. Therefore, it will be necessary to develop products that capture the actual situation of consumers. In this report, we will explain the remarkable consumer values and the actual situation of hair care found out from quantitative surveys, the basic knowledge about the structure and characteristics of hair, and hair evaluation methods, using actual development examples.

Based on several studies, cosmetics that focus on the care of the area from the neck to the clavicle have been released. Most of them focus on wrinkles in the neck area due to aging and ultraviolet rays, and various research findings have been obtained. However, evaluation limited to the neck area has not revealed a definitive cause directly linked to wrinkle formation. In addition, there is little knowledge on the relationship between wrinkles on the neck and changes in the physiological functions of the skin in the neck and surrounding areas. In this study, we examined the relationship between the degree of wrinkles on the neck and skin measurements in the surrounding area in 32 healthy women aged 25-54 yrs. The results showed that the water content of the clavicle stratum corneum did not correlate with age. Furthermore, the water content of the clavicle stratum corneum in the group with less noticeable neck wrinkles was significantly higher than that with more noticeable wrinkles, and it was found to be maintained at a relatively constant level. These findings suggest that neck wrinkles are closely related to the water retention capacity in the clavicle skin, and that age is not the primary factor in this relationship. Understanding the changes in the physiological parameters of the clavicle skin is important for the care of wrinkles in the neck region.

Cellulose nanofiber (CNF), which is used in various cosmetics as a rheology control agent, has various functions such as thickening effects. One of the functions of CNF is to form Pickering emulsion. However, it has been unclear under what conditions CNF can emulsify in cosmetic formulations that contain a wide variety of ingredients. In the present study, we investigated the relationship between the emulsifying ability of CNF and the type of oil and the ingredients added to the aqueous phase, and searched for the emulsifiable range of CNF. First, we investigated the emulsifiable oils. The possibility of emulsification was plotted on an organic conceptual diagram based on the structure of the oils. The results showed that CNF could emulsify relatively low polarity oils with a ratio of inorganic to organic values of less than 0.25. Next, we investigated the effects of the addition of ethanol or polyols into the aqueous phase on interfacial tension and emulsification. As a result, the higher the additive concentration, the lower the interfacial tension. Furthermore, it was found that the decrease in the interfacial tension due to the additives made emulsification difficult even for the oils that were originally emulsifiable. In other words, the emulsification ability of CNF was reduced by the addition of water-soluble additives.

Ceramides are principal components of intercellular lipids and play important roles for skin moisturization and barrier function. However, it is difficult to dissolve ceramides in aqueous formulations such as cosmetic lotion because of their high hydrophobicity and crystallinity. For this reason, various encapsulation technologies for incorporating ceramides into lotion have been reported. Since the outer surface of these capsules is hydrophilic, their affinity for skin was not fully considered. Therefore, we focused on hexosome to develop a new ceramide-containing capsule with consideration of affinity for skin. Hexosome is a capsule with a hydrophobic surface, formed by nano-dispersion of reversed hexagonal liquid crystals (H₂). Because of this structural characteristic, hexosome can be expected to efficiently penetrate to the skin (stratum corneum). However, hexosome is a hydrophobic capsule that aggregates immediately in lotion. To solve this problem, studies using poloxamer as a key ingredient (dispersant) have been reported, but no other dispersants have been well studied. Additionally, petroleum-derived materials such as poloxamer tend to be not preferred by consumers, due to the recent global trend of favoring plant-derived materials for cosmetics. Therefore, we have developed a new ceramide-containing hexosome (Cer-Hexosome) stabilized by a plant-based dispersant. First, the structure of the developed Cer-Hexosome was confirmed with small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (Cryo-TEM). Next, the skin permeation amount of ceramide was quantified by LC/MS, and it was confirmed that the ceramide permeation effect of hexosome was 1.5 times that of liposome. Then, in a one-month continuous use test, it was confirmed that Cer-Hexosome significantly improved the barrier function of the skin. Finally, the effect on intercellular lipids of the human stratum corneum was analyzed by wide-angle X-ray diffraction (WAXD), and it was confirmed that Cer-Hexosome enhances the orthorhombic structure.

Increasing and retaining the water content of the stratum corneum (SC) is an important function of skincare products, for which emulsions may be a promising solution. Various technologies for emulsion preparation have been reported, but methods to control and thus improve emulsion functionality are currently lacking. In this study, we investigated suitable formulations to control the arrangement of the main components of emulsions (oils and water) when they are applied to the skin surface, to help improve and retain SC hydration. The oily components exhibited low permeability and a high occlusive effect when the emulsified particles were enlarged. The use of solid oil was also effective for thorough occlusion as it prevented oil components from falling into the skin grooves. Water tends to lie on top of the oil component layer, but the oil holding capacity of the hydrated clay minerals prevented this phenomenon and allowed water to reach the skin surface. Based on these results, we prepared a prototype clay mineral-structured large solid oil emulsion and confirmed that the prototype improved SC hydration. This study demonstrated the importance of the specific arrangement of the emulsion components when applied to the skin for the improvement of SC hydration.

W/O emulsions using silicone are used in cosmetics because they are water resistant, spread well and are not sticky. Organoclay is a useful thickener that forms a thixotropic oil gel with polarized materials such as surfactants. But its viscosity changes with the surfactant's amount. Disteardimonium hectorite is generally used in cosmetics. Since it is modified with a long-chain alkyl group, it is incompatible with silicone oil. Therefore, a silicone surfactant is used for silicone-based W/O emulsions with organoclays. Water, oil and powder are used in liquid foundations, there are many interfaces. The interfaces also affect the function of surfactants and thickeners. Therefore, in formulation design, it is difficult to understand why changes in viscosity and stability are caused. This study first investigated the thickening mechanism of silicone oil gels. Next I studied how a silicone surfactant affects the viscosity of W/O emulsions containing organoclays. As a result, I discovered that W/O emulsion viscosity becomes maximum a certain amount of the surfactant and is not easily affected by the storage temperature. However, if the surfactant's amount exceeds that amount, the thickening mechanism is interfered with and a high-viscosity emulsion cannot be obtained. When the emulsion with the excess amount of the surfactant is kept at high temperatures, the interference disappears and the emulsion viscosity becomes high.

Scent affects our mind and body, so that it plays an important role in cosmetics. It is difficult to understand which components in scent affect dominantly, because scent contains many components with low concentrations. Gas chromatography mass spectrometry (GC/MS) has been widely used for scent analysis: however, this method requires sample preparation and accumulation over some periods of time, meaning that we cannot trace instantaneous change in the concentration of each component. Furthermore, since scent components contain many structural isomers as represented by monoterpenes, it is also important to distinguishably measure isomers in real time in scent research. In this study, atmospheric pressure corona discharge ionization (APCDI) coupled with collision-induced dissociation mass spectrometry (CID-MS) was used to develop a method to distinguish monoterpene isomers (C₁₀H₁₆) in real time. Three monoterpene isomers（i.e., α-pinene, limonene and myrcene） were protonated instantaneously, and then were selected as precursor ions at product-ion scan and as monitoring ions at precursor-ion scan. In the case of product-ion scan, similar product ions (e.g., C₆H₉⁺ at m/z 81 and C₇H₁₁⁺ at m/z 95) were observed for all the analytes. These results are likely attributable to the isomers having similar structure to protonated molecules. In contrast, precursor-ion spectra showed a specific pattern for each isomer, which can result from the difference in formation of covalent-bonded and/or hydrogen-bonded dimers depending on isomeric structure. Consequently, it was found that precursor-ion scan is useful for identification of monoterpene isomers in real time.

Changes in the chemical composition of the hair surface due to damage can be analyzed using infrared spectroscopy. However, since hair damage repair is performed at the solid-liquid interface, it is important to evaluate the surface properties in a water-containing state in order to understand the interaction with the repair agent. That is, if the zeta potential on the hair surface can be evaluated easily and reproducibly, it will lead to quantification of hair damage and can be used as a screening method for the repairing effects of various reagents on hair. Therefore, in this study, we evaluated the surface characteristics of bleached hair in liquid and tracked the adsorption behavior of cationic cellulose by zeta potential measurement using the streaming potential method as the measurement principle. It was possible to quantify damage because there was a high correlation between the bleaching time, the absorbance of the wave number derived from cysteic acid by ATR, and the isoelectric point obtained from the pH-dependent curve of the zeta potential. In the tracking of the adsorption behavior of cationic cellulose, there was a negative correlation between the bleaching time and the adsorption rate, suggesting that the degree of adsorption of the repair agent can be estimated using the streaming potential method.