For many people suffering from frizzy hair, hair straightening technologies based on reduction and oxidation reactions using thioglycolic acid and hydrogen peroxide play an important role in solving their problems. However, it is known that there is more or less hair damage caused by oxidation after reduction and heat treatment. Over the past decade, a number of new frizzy hair control technologies have been developed to replace the hair straightening technologies. These have even led to the birth of a new category of “acid/heat treatments” which utilizes the heat of a hair iron and specific acids as functional ingredients. Among these, technologies using α-keto acids, especially glyoxylic acid (GA), have been highly evaluated in the market. However, there are few reports on the mechanism of action of GA, and there is no information on the type of cross-links produced, their position in the microstructure, the amount of cross-linking, or even the change in the hair structure. In this report, we present the mechanism of frizzy hair suppression as considered from the characteristic morphological changes and stress-strain properties of hair obtained by GA/heat treatment.

Ceramides are major components within the intercellular lamella of the stratum corneum and play an important role in the barrier function of skin. Thus, cosmetic products containing ceramides are expected to maintain and improve the skin barrier. However, maintaining the stability of ceramides within cosmetic products remains a challenge owing to their high crystallinity. Our previous study demonstrated a promising method for the incorporation of ceramides into a lotion via complexation with nonionic surfactant vesicles (i.e., niosomes). However, the stable complexation of ceramides within niosomes may interfere with their beneficial properties, because ceramides improve the skin barrier via lamella formation. Consequently, the skin moisturizing effect of the ceramide-complexed niosomes (CCNs) was insufficient. Thus, it was hypothesized that the properties of ceramide could be maximized by encouraging the collapse of the CCNs upon contact with the stratum corneum. The destabilization of nanoparticles is often achieved using stimuli-responsive polymers, which change their hydrophobicity depending on the external environment and disrupt the nanoparticle structure through hydrophobic interaction. A range of pH and temperature dual-responsive polymers (poly(MD-MAA-LT)s) was been developed in our previous study, and is responsive to the slightly acidic pH and moderately high temperature of human skin. In this study, we construct pH and temperature dual-responsive CCNs (Res-CCNs) through the modification of the CCNs with poly (MD-MAA-LT) s. The Res-CCNs were stable throughout a wide temperature range of 5 to 50°C when held at a constant pH of 6.5. However, the size of Res-CCNs increased significantly when the temperature was increased under the slightly more acidic conditions of human skin (pH of 5.0), which led to the release of ceramide. In addition, Res-CCNs showed a moisturizing effect for an extended period, when applied on human skin. This novel approach to the application of ceramides is expected to promote the benefits of ceramides in the skin care field.

Hair diameter is one of the most basic hair properties and is considered to be closely related to sensory evaluation of a hair bundle: however, the fluctuation of hair diameter in the length direction has not been studied very much. In this study, the fluctuation of hair diameter in the length direction was measured with the cross section of the hair as an elliptical shape, and the relation with the sensory evaluation was investigated. Precise and two-dimensional fluctuation of hair diameter was expressed for the first time in the form of “hair diameter profile” from the data that measured 400 points of hair diameter at intervals of 0.125 mm in the length direction of the hair. It was found that the hair diameter fluctuated by 3.8% on average even in a strand of hair, and the major axis angle also changed. Therefore, the torsional hair was visually and quantitatively expressed using a parameter of the accumulated major axis angle. As the result of acquiring hair diameter profiles and sensory evaluation on four types of hair with different characteristics, the larger the standard deviation of the average diameter and the degree of the major axis angle, the lower the scores of various sensory evaluations were found to be. There was a certain correlation between the hair diameter profile and the sensory evaluation, which suggested that hair diameter profile might be useful to evaluate total hair characteristics.

Due to the spread of COVID-19, it has become necessary to wear face masks for long periods of time. Therefore, we decided to characterize changes in skin properties that result from the long-term wearing of face masks. In this study, we measured the temperature and humidity environment inside face masks and investigated changes of skin properties due to wearing face masks for a long time. In addition, as potential causes of any changes, we evaluated whether the temperature and/or humidity environment inside face masks affects the quality of the stratum corneum. The results demonstrate that the skin inside face masks is exposed to a hot and humid environment throughout the day and that sudden changes of temperature and humidity occur when face masks are removed. Wearing a face mask with a mild exercise load even for as little as 30 min has been shown to induce a change in the quality of the stratum corneum. A comparison of skin conditions between outside and inside face masks reveals that continuous wearing of face masks made the skin sensitive, increased keratinization and decreased the barrier function. In addition, the results suggest that “rubbing” occurs on a wide area of the skin inside face masks and the skin becomes covered with sebum containing a high ratio of free fatty acids.

Hair medulla is a porous structure at the centre of the hair, of which little is known, particularly its functions. We have shown that the structure of medulla can be altered by applying and penetrating into the hair, a formulation comprising a combination of specific components. Such a chemical treatment lends glossiness to the hair, making it aesthetically attractive. We call this process Hair Medulla Care. In this study, we investigated further by assessing the extent of penetrability of substances in relation to their chemical properties. The results showed that the Hair Medulla Care enhances penetration of all substances that we attempted, anionic, cationic and lipophilic fluorescent dyes. This finding can be applied to basic hair dyes, enabling them to penetrate deeply into the hair, creating deeper and more vivid colours. Its dyeing ability was far beyond what can be expected from conventional means. Furthermore, it allowed the infiltration of melanin into the hair, which was impossible until now. Thus, the procedure can deliver various substances which have different properties to the medulla and can be applied for various hair care and cosmetic products, such as damage care and perms, in addition to hair colours.

Nursing care odor is a complex odor composed of strong malodors such as fecal and body odor. We have succeeded in developing novel deodorant fragrances for it that can significantly reduce discomfort by combining Olfactory Receptor (OR) and harmonizing technologies. Firstly, OR2L3 was found as the receptor to the fecal odor key components such as skatole and indole for the first time and then antagonists of it were discovered from fragrance materials. Next, to utilize the harmonizing technology that can change malodors into pleasant odors, we searched for essential oils that have a high harmonizing effect with the fecal odor by sensory evaluation. Finally, it was demonstrated that the combination of the technologies could greatly reduce the discomfort of the nursing care odor. Thus, it was verified that this complementary combination of the technologies could develop more effective deodorant fragrances for complex malodors. It can be expected that the deodorant fragrances developed in this study will relieve stress for both caregivers and care-receivers by reducing the discomfort of the nursing care odor, thereby it makes them healthier physically and mentally, leading to improvements in QOL.

Currently, shampoo products are combined anionic surfactants, amphoteric surfactants and cationic polymer in order to give a smooth texture to the hair surface. These substrates are generated by coacervation in the washing and rinsing processes. However, the relationship between the physical properties of coacervation and the tactile texture has not been uncovered. In this study, we demonstrated characteristics of coacervation and tactile texture in amino acid-type surfactant, amphoteric surfactant and cationic polymer systems. In these results, it is shown that tactile texture and physical properties depend on the variety of amphoteric surfactants. The characteristic tactile textures created by replacing amphoteric surfactants were smooth, moist, and resilient. Furthermore, it was confirmed that the physical properties were different in the coacervation obtained by various formulations. These findings suggest that the features of the generated coacervation influenced the tactile texture.

Titanium dioxide (TiO₂) nanoparticles have been used as ultraviolet light scattering agents in sunscreen cosmetics. However, they tend to self-aggregate due to their high surface energies and strong interparticle attraction in water. In this research, we focused on liquid surface plasma (LSP), and studied the water dispersion technology of fine-particle TiO₂. The plasma formed is considered to generate shock waves and species such as O radicals, which have high oxidation potential, around the liquid surface. The LSP treatment enabled preparation of the aqueous dispersions with 10% (wt) TiO₂ nanoparticles that have approximately 100 nm particle size and long-term stability. In addition, from the chemical analyses of the dispersions, Al compounds derived from the underwater Al electrode were formed on the TiO₂ surface. It was clear that TiO₂ nanoparticles had high positive charge under pH neutral condition due to Al compounds on the surface, so that the dispersions were stabilized by electrostatic repulsion between the particles. Furthermore, from the X-ray absorption fine structure (XAFS) measurements, it was found that the chemical state and molecular structure of Ti were not altered by the LSP treatment, and amorphous aluminum hydroxide (Al(OH)₃) was detected on the surface. These findings suggest that the TiO₂ aqueous dispersion obtained by the LSP treatment can be safely applied to cosmetics. Finally, a composite powder (PLD-TiB), which is BaSO₄ covered with TiO₂, was obtained by electrostatic combination in aqueous dispersion. From the SEM image, it was observed that the BaSO₄ surface was uniformly coated with TiO₂. Due to the uniform coating without aggregation, PLD-TiB had a great UV protecting effect and a smooth feeling on the skin.