The tactile sensation of cosmetics is one of the important sensibility values that affect the purchase and preference of products. In the evaluation of the tactile sensation of cosmetics up to now, the method of examining the relation between sensory evaluation and physical properties including rheology characteristics has been common. However, a method of evaluating the time change of touch from the beginning of applying cosmetics to the skin until it becomes familiar was not common. Because the tactile sensation is recognized through the active movement of “touching”， it is necessary to examine dynamic behavior between finger, formulation and skin when the person is touching the skin. Therefore, we measured the finger motion and examined the relation to the tactile sensation during application of cosmetics. In this paper, we first outline the definition of tactile sensation, as well as its perception and cognitive mechanisms. Next, after explaining the inertial sensor that can be attached to the finger that we have developed, findings and application examples that examine the relationship between finger motion and the tactile sensation of cosmetics will be described.

The application of sunscreens is very important to protect skin from premature aging and photodamage. The most common sunscreens on the market contain synthetic ultraviolet (UV) filters, which are known to have potential toxicity in humans. The development of natural sunscreen agents such as herbal/botanical extracts is of contemporary interest, because their safety would be widely accepted by consumers. In this study, extracts from olive fruit, leaves, branches and bark were tested for sunscreen activity, and olive bark extract (OBE) was found to show effective sunscreen and anti-skin-aging activity. The in vitro sun protection factor (SPF) values of four extracts obtained from olive ingredients were evaluated by UV spectrophotometry. Among the tested extracts, OBE showed the highest SPF value of 10.00. The SPF value varied in a concentration-dependent manner. The critical wavelength of OBE was greater than 370 nm, indicating broad protection against UVB and UVA, making it a so-called “broad spectrum” UV absorber. Accelerated stability and in vitro photoprotective efficacy assessment, including UV irradiation, heating, exposure to a wide pH range (from acidic to alkaline), and freeze-thaw cycles, revealed that the sunscreen activity of OBE was physicochemically stable. OBE increased cell survival in primary human keratinocytes after UVB irradiation. OBE was polyphenol-rich, presenting high antioxidant activity, which counters free radical species that are the main cause of numerous negative skin changes. OBE showed strong anti-skin-aging activity by inhibiting dermal enzymes such as collagenase and hyaluronidase, and promoting skin fibroblast proliferation. OBE inhibits α-melanocyte stimulating hormone-induced melanogenesis in B16 melanoma cells. Thus, OBE could play multiple roles in skincare, and could be incorporated not only into sunscreens, but also into daily care and skin lightening products. The combination of these protective and preventive characteristics recommends OBE as a cosmetic agent and a possible active ingredient of sunscreen formulations.

Intercellular lipids of the stratum corneum form a lamellar structure, and perform as a protective interface between the human body and external environment. Ceramide is the major component of intercellular lipid and plays an important role in the barrier function of skin. Therefore, a high content of ceramide in cosmetics can be expected to improve the barrier function of skin. However, it is very difficult to make cosmetics containing highly concentrated ceramide since ceramide has high crystallinity in water or in oil. For these reasons, many studies about the ceramide formulations have been conducted on aqueous systems. For example, it is well known that the ceramide formulations with a lamellar structure such as α-gel or liquid crystal improve the barrier function of skin especially well. However, few studies have been done on oily systems. In this study, we attempted to compound ceramide into oily systems with a lamellar structure, and finally it was found that the ceramide was dissolved in non-polar oil by forming a stable organogel with lamellar structure in the presence of meadowfoam estlide. Furthermore, a stable oily cosmetic with a high content of ceramide was prepared by dispersing this gel into oil, and the oily cosmetic had a remarkable improvement effect on the barrier function of skin.

Sunlight includes ultraviolet (UV) light, visible light and near-infrared (NIR) light. Recent studies have shown that not only UVA but also blue light (BL) and NIR accelerate the photoaging symptoms of skin associated with fiber depletion of collagen and elastin in the dermis. In this study, we examined the influence of UVA, BL and NIR on the reconstruction of elastic fibers by measuring mRNA expression of elastic fiber related proteins and fluorescence immunostaining of Fibrillin-1. UVA, BL and NIR increased intracellular ROS of cultured human fibroblasts, and showed suppression of construction and enhancement of decomposition in elastic fiber. On the other hand, 3-O-glyceryl ascorbate (VC-3G) which is an ascorbic acid derivative and possesses antioxidative property, suppressed the elevation of intracellular ROS and restored the mRNA expression levels of elastic fiber related proteins and incomplete construction of elastic fiber induced by UVA, BL and NIR. Taken together, we conclude that VC-3G is an effective derivative of ascorbic acid to prevent depletion of elastic fibers initiated by solar light.

In recent years, the common appealing points of body soap have been “moistening the skin”, “mild to the skin” and “lasting fragrance”. According to our survey, we found that many women place importance on the moisturizing effect when purchasing body soap. However, more than half of consumers cannot actually feel the moisturizing effect. We considered the possibility that the moisturizing ingredients were washed off easily so that it was difficult to realize the moisturizing feeling. Therefore, we developed a body soap containing moisturizing ingredients which tend to remain on the skin by utilizing a complex of an anionic surfactant and a cationic polymer. Moreover, we clarified that the complex was retained on the skin surface after washing to express a suppressing effect on water loss from the skin. As a result, the complex provides a body soap having high moisturizing effect and moisturizing feeling.

Dihydroxyacetone (DHA) is used as the main agent of self-tanning formulations. However, it is difficult to formulate DHA with high content because of its very high reactivity and instability, and it is known that coloring strength has been increased by using polyhydric alcohol in combination up to now. In this study, we investigated improving coloring strength in vitro and in vivo using water-soluble components including polyhydric alcohol. As a result, Methyl gluceth-10 (MG-10) was most effective in vitro. In contrast, MG-10 alone was the most ineffective in vivo. However, it was revealed that the coloring strength was improved by mixing with ethanol. We thought that ethanol distrubs the lamellar structure in the stratum corneum, shakes the intercellular lipid structure, and makes skin permeation easier, whereas the molecular weight was so large that it could not penetrate the skin alone. We focused on the polyethylene glycol (PEG) structure in MG-10, and changed the PEG chain length in vitro to confirm the coloring effect. Furthermore, as an additional test, the number of oxygen atoms in the solution was adjusted to PEG-40 and made constant, and the coloring effect was confirmed. As a result, in the test in which the number of moles of PEG was constant, it was found that the coloring effect was improved as the chain length of PEG became longer. On the other hand, in the test in which the number of oxygen atoms in the solution was constant, the same absorbance was obtained uniformly. From these results, it was thought that the oxygen in the PEG chain contributed to the coloring effect. Furthermore, MALDI/MS measurement and FT-IR measurement suggested that oxygen atoms in the PEG chain plays the role of mediator via its hydrogen bond with the amino acid and DHA.

Hair can be exposed to oxidative environments such as hydrogen peroxide in hair dyes and bleaching agents, ultraviolet (UV) ray irradiation from sunlight, catalytic conditions with heavy metal compositions, and oxidative air pollutants. Therefore, unsaturated fatty acids present in the hair could be oxidized to form lipid peroxides and finally converted to aldehydes as their end products. Lipid peroxides and aldehydes will cause hair damage at the molecular level by denaturing hair proteins, and furthermore most of the short-chain aldehydes are sources of malodor. In the present study, we identified and quantified volatile aldehydes generated from hair by UV irradiation. Fatty acids in the hair samples were analyzed by GC-MS and 13 kinds of them detected, the ratio of saturated to unsaturated being 1:2. The hair was irradiated with UV light (total amount 706.8 kJ/m²) in a closed container, so that the generated gas was directly trapped in a solution of 1,3-cyclohexanedione (CHD). The resulting aldehyde-CHD derivatives were analyzed by LCMS. Short-chain aldehydes, formaldehyde, acetaldehyde and propanal were detected, and the amounts of them generated from 100 g of hair were 3.3, 0.3 and 0.1 mg, respectively. These low molecular weight aldehydes may have been formed by the consecutive degradation (called Norrish type II reaction) of the long-chain aldehydes which are produced by oxidative cleavage of double bonds in the unsaturated fatty acids in the hair.