Color treatment is a hair dying agent which can both treat and color hair. Unlike hair color, which mixes 2 agents before use, color treatment cannot lighten hair color by an application and change hair color greatly. But from its convenience and a sense of security, it has been attracting attention as an item which takes the place of hair color or supports the effect of it. This review describes dye stuffs and their characteristics used in general color treatment, as well as the coloring mechanism and agent characteristics. Additionally, the development and technology of a hair dying agent which contains dihydroxyindole, a black melanin precursor, and its characteristics are described.

A keratotic plug (KP) is a solid mass primarily composed of protein that forms in pores, and preventing their formation has been challenging. The presence of keratin 17 (K17), a characteristic of KPs, implies the involvement of interferon-gamma (IFN-γ), which contributes to K17 formation, in KP formation. IFN-γ is also involved in the production of nitric oxide (NO), and NO-mediated nitration of tyrosine is known to induce protein aggregation, which is one of the possible mechanisms by which proteins become solids. In this study, to clarify the involvement of IFN-γ and protein nitration in KPs, we investigated the relationship between the amount of IFN-γ collected from the skin around nasal alae and the number of KPs, protein components of KPs, and the effect of nitration on molecular sizes of proteins in vitro. As a result, more KPs were detected in individuals with high IFN-γ levels, and nitrotyrosine was present within the KPs. Protein nitration increased the molecular size of proteins, and IFN-γ increased nitrotyrosine production in keratinocytes in the same manner as in NO donors. Collectively, these findings indicate that IFN-γ-mediated protein nitration via NO generation causes solid mass formation in the pores. Inhibition of protein nitration followed by protein aggregation could be effective in preventing KP formation.

The importance of handwashing has become widespread among consumers due to the increased awareness of hygiene following the spread of COVID-19 and awareness-raising activities by the government. However, as a result of a consumer survey, we confirmed that people want to know the antibacterial and antiviral sustainability after handwashing. In this study, we set up a model experimental system assuming the risk of contamination after handwashing, and measured the antibacterial and antiviral effects of different surfactants. As a result of our investigation, the number of viable bacteria was high on public doorknobs and the frequency of touching them was also high. Therefore, assuming the behavior of touching a doorknob four times an hour, we measured the antibacterial and antiviral effects by quantifying the amount of remaining bacteria or viruses when the bacterial or viral solution was applied to the washed model skin every 20 min. The results showed that washing with fatty acid salts decreased the residual amount of bacteria and viruses even after repeated applications, suggesting that the antibacterial and antiviral effects were highly sustained. We consider both deactivating performance and the remaining of surfactant may affect the persistence of antibacterial and antiviral effects.

Cationic surfactants are formulated in various hair care products, including hair treatments, because they tend to smooth the hair's surface through adsorption. Many studies have been reported on the adsorption behavior of cationic surfactants on the hair's surface, as well as their effects on the hair. On the other hand, while it is also known that cationic surfactants penetrate into the hair, few studies have investigated their effects on the hair. Therefore, we investigated the effects of permeating the cationic surfactant alkyl trimethyl ammonium chloride into the hair. As a result, we found that alkyl trimethyl ammonium chloride has the effect of expanding hair. Further experiments found that dodecyl trimethyl ammonium chloride (DTAC) with an alkyl chain length of 12 is highly effective at expanding hair in a short treatment time. From a quantitative analysis of DTAC in hair, we clarified that the hair expansion by DTAC mainly results from the large amount of DTAC absorbed into the hair. In addition, hair treated with DTAC showed an increase in flexural rigidity and a repair of the distorted cross-sectional shape caused by damage. These results suggest that DTAC has great potential for future hair care products.

Sugar alcohols in the raw ingredients for cosmetics are recognized as moisturizers for skin and hair care. While some sugar alcohols, such as sorbitol and xylitol, are widely used, there is far less use made of sugar alcohols than polyhydric alcohols (e.g., glycerin) with similar molecular structures. This study focuses on monosaccharide sugar alcohols to verify their texture and moisturizing properties, which are regarded as important in leave-on cosmetics. Using experimental skin lotion with different monosaccharide sugar alcohols or with glycerin as a comparison target, first, texture was evaluated by sensory evaluations and by measurement with instruments. Monosac-charide sugar alcohols showed different results from glycerin for texture items such as brake sensation immediately before drying, no stickiness after drying, refreshment, and moisture. There was also considerable variation between the different monosaccharide sugar alcohols. Next, stratum corneum moisture content was measured, and variation in moisturizing ability between the different monosaccharide sugar alcohols was confirmed. Of notable interest are the differences in texture and moisturizing properties found between formulations even when the components had similar molecular structures. Based on the results of this study, the use of different monosaccharide sugar alcohols to suit the various product concepts of leave-on cosmetics is expected to make a significant contribution to product design.

Several ways have been reported to enhance the penetration of cosmetic ingredients into the stratum corneum through electrical waveforms. We recently developed the complexed penetration waveform, Multi Spike Moist Pulse (MSMP) which includes electroporation and radiofrequency factors. Our experimental results show that MSMP is the most effective electrical waveform pattern in two different (positive/+ or negative/-) chemical structures. (1) We confirmed that iontophoresis (+/-)showed a higher tendency in penetration than the control, but no significant difference was found between these waveforms and the control. And radiofrequency showed a higher penetration than the control in a positive/+ structure. (2) We showed that MSMP promotes a higher transdermal absorption of nicotinamide than the rectangular wave under the same energy intensity. Therefore, it is concluded that MSMP can promotes the higher absorption of cosmetic ingredients in an effective way.